Fix(presto)!: generate "SUBSTR" instead of "SUBSTRING" for Substr expr

[georgesittas]

Fixes #7581

[github-actions]

SQLGlot Integration Test Results

Comparing:

• this branch (sqlglot:jo/substr_rename, sqlglot version: jo/substr_rename)
• baseline (main, sqlglot version: 0.0.1.dev1)

By Dialect

dialect	main	sqlglot:jo/substr_rename	transitions	links
bigquery -> bigquery	24647/24652 passed (100.0%)	23497/23497 passed (100.0%)	No change	full result / delta
bigquery -> duckdb	867/1154 passed (75.1%)	0/0 passed (0.0%)	Results not found	full result / delta
duckdb -> duckdb	5823/5823 passed (100.0%)	0/0 passed (0.0%)	Results not found	full result / delta
snowflake -> duckdb	1063/1961 passed (54.2%)	0/0 passed (0.0%)	Results not found	full result / delta
snowflake -> snowflake	65133/65133 passed (100.0%)	63027/63027 passed (100.0%)	No change	full result / delta
databricks -> databricks	1370/1370 passed (100.0%)	1370/1370 passed (100.0%)	No change	full result / delta
postgres -> postgres	6042/6042 passed (100.0%)	6042/6042 passed (100.0%)	No change	full result / delta
redshift -> redshift	7101/7101 passed (100.0%)	7101/7101 passed (100.0%)	No change	full result / delta

Overall

main: 113236 total, 112046 passed (pass rate: 98.9%), sqlglot version: 0.0.1.dev1

sqlglot:jo/substr_rename: 101037 total, 101037 passed (pass rate: 100.0%), sqlglot version: jo/substr_rename

Transitions:
No change

Dialect pair changes: 0 previous results not found, 3 current results not found

✅ 38 test(s) passed