Fix markdown lint issues in postgresql.md

[kadler]

postgresql.md:3:81 MD013/line-length Line length [Expected: 80; Actual: 233]
postgresql.md:7:81 MD013/line-length Line length [Expected: 80; Actual: 206]
postgresql.md:10:1 MD014/commands-show-output Dollar signs used before commands without showing output [Context: "$ yum install postgresql12-ser..."]
postgresql.md:13:81 MD013/line-length Line length [Expected: 80; Actual: 355]
postgresql.md:17 MD040/fenced-code-language Fenced code blocks should have a language specified [Context: "```"]
postgresql.md:19 MD031/blanks-around-fences Fenced code blocks should be surrounded by blank lines [Context: "```"]
postgresql.md:22:81 MD013/line-length Line length [Expected: 80; Actual: 119]
postgresql.md:25:1 MD014/commands-show-output Dollar signs used before commands without showing output [Context: "$ mkdir /home/postgres"]
postgresql.md:26:1 MD014/commands-show-output Dollar signs used before commands without showing output [Context: "$ chown postgres /home/postgre..."]
postgresql.md:27 MD031/blanks-around-fences Fenced code blocks should be surrounded by blank lines [Context: "```"]
postgresql.md:32:81 MD013/line-length Line length [Expected: 80; Actual: 100]
postgresql.md:34:81 MD013/line-length Line length [Expected: 80; Actual: 107]
postgresql.md:38:1 MD014/commands-show-output Dollar signs used before commands without showing output [Context: "$ export PGDATA=/home/postgres"]
postgresql.md:40:1 MD014/commands-show-output Dollar signs used before commands without showing output [Context: "$ initdb -E UTF-8 -D /home/pos..."]
postgresql.md:45:81 MD013/line-length Line length [Expected: 80; Actual: 94]
postgresql.md:48 MD031/blanks-around-fences Fenced code blocks should be surrounded by blank lines [Context: "```"]
postgresql.md:48 MD040/fenced-code-language Fenced code blocks should have a language specified [Context: "```"]
postgresql.md:58:1 MD014/commands-show-output Dollar signs used before commands without showing output [Context: "$ pg_ctl -D /home/postgres -l ..."]
postgresql.md:62 MD031/blanks-around-fences Fenced code blocks should be surrounded by blank lines [Context: "```"]
postgresql.md:62 MD040/fenced-code-language Fenced code blocks should have a language specified [Context: "```"]
postgresql.md:68 MD031/blanks-around-fences Fenced code blocks should be surrounded by blank lines [Context: "```bash"]
postgresql.md:69:1 MD014/commands-show-output Dollar signs used before commands without showing output [Context: "$ pg_ctl -D /home/postgres -l ..."]
postgresql.md:72:81 MD013/line-length Line length [Expected: 80; Actual: 113]
postgresql.md:73 MD031/blanks-around-fences Fenced code blocks should be surrounded by blank lines [Context: "```"]
postgresql.md:73 MD040/fenced-code-language Fenced code blocks should have a language specified [Context: "```"]
postgresql.md:85:81 MD013/line-length Line length [Expected: 80; Actual: 188]
postgresql.md:86 MD031/blanks-around-fences Fenced code blocks should be surrounded by blank lines [Context: "```"]
postgresql.md:86 MD040/fenced-code-language Fenced code blocks should have a language specified [Context: "```"]
postgresql.md:88:57 MD009/no-trailing-spaces Trailing spaces [Expected: 0 or 2; Actual: 19]
postgresql.md:90:28 MD009/no-trailing-spaces Trailing spaces [Expected: 0 or 2; Actual: 48]
postgresql.md:91:64 MD009/no-trailing-spaces Trailing spaces [Expected: 0 or 2; Actual: 12]
postgresql.md:92:18 MD009/no-trailing-spaces Trailing spaces [Expected: 0 or 2; Actual: 58]
postgresql.md:93:1 MD009/no-trailing-spaces Trailing spaces [Expected: 0 or 2; Actual: 75]
postgresql.md:94:40 MD009/no-trailing-spaces Trailing spaces [Expected: 0 or 2; Actual: 36]
postgresql.md:95:62 MD009/no-trailing-spaces Trailing spaces [Expected: 0 or 2; Actual: 14]
postgresql.md:96:63 MD009/no-trailing-spaces Trailing spaces [Expected: 0 or 2; Actual: 13]
postgresql.md:105:81 MD013/line-length Line length [Expected: 80; Actual: 108]
postgresql.md:107 MD040/fenced-code-language Fenced code blocks should have a language specified [Context: "```"]
postgresql.md:123:12 MD009/no-trailing-spaces Trailing spaces [Expected: 0 or 2; Actual: 3]
postgresql.md:131:81 MD013/line-length Line length [Expected: 80; Actual: 96]
postgresql.md:133 MD040/fenced-code-language Fenced code blocks should have a language specified [Context: "```"]
postgresql.md:135:28 MD009/no-trailing-spaces Trailing spaces [Expected: 0 or 2; Actual: 1]
postgresql.md:140:12 MD009/no-trailing-spaces Trailing spaces [Expected: 0 or 2; Actual: 3]
postgresql.md:149:81 MD013/line-length Line length [Expected: 80; Actual: 121]
postgresql.md:151 MD040/fenced-code-language Fenced code blocks should have a language specified [Context: "```"]
postgresql.md:161:81 MD013/line-length Line length [Expected: 80; Actual: 133]
postgresql.md:163:81 MD013/line-length Line length [Expected: 80; Actual: 195]
postgresql.md:165:81 MD013/line-length Line length [Expected: 80; Actual: 86]
postgresql.md:168:1 MD014/commands-show-output Dollar signs used before commands without showing output [Context: "$ pg_ctl -D /home/postgres -l ..."]
postgresql.md:171:81 MD013/line-length Line length [Expected: 80; Actual: 173]
postgresql.md:173 MD040/fenced-code-language Fenced code blocks should have a language specified [Context: "```"]
postgresql.md:176 MD031/blanks-around-fences Fenced code blocks should be surrounded by blank lines [Context: "```"]
postgresql.md:179:81 MD013/line-length Line length [Expected: 80; Actual: 128]
postgresql.md:183 MD040/fenced-code-language Fenced code blocks should have a language specified [Context: "```"]
postgresql.md:198:1 MD014/commands-show-output Dollar signs used before commands without showing output [Context: "$ pg_ctl -D /home/postgres -l ..."]
postgresql.md:201:81 MD013/line-length Line length [Expected: 80; Actual: 145]