chore: add missing newlines to source header & remove empty comment lines

[cakebaker]

A follow-up to #14572. The command/script used there missed some missing newlines. And sometimes the addition of a newline led to a useless empty comment line.

[github-actions]

GNU testsuite comparison:

Skip an intermittent issue tests/cut/bounded-memory (fails in this run but passes in the 'main' branch)
Skip an intermittent issue tests/tail/inotify-dir-recreate (fails in this run but passes in the 'main' branch)
Skip an intermittent issue tests/tail/tail-n0f (fails in this run but passes in the 'main' branch)
Congrats! The gnu test tests/seq/seq-epipe is now passing!

[xtqqczze]

Thanks