issue template: Add '\n' to the end of environment output

It will be much convenient to copy output of the script
without touching of bash prompt at the last line of the
output.

.github/ISSUE_TEMPLATE.md

@@ -2,7 +2,7 @@

Replace this with the output of:

`printf "$(rkt version)\n--\n$(uname -srm)\n--\n$(cat /etc/os-release)\n--\n$(systemctl --version)"`
`printf "$(rkt version)\n--\n$(uname -srm)\n--\n$(cat /etc/os-release)\n--\n$(systemctl --version)\n"`

**What did you do?**