[TASK] Replace deprecated egrep in commit-msg hook

egrep is deprecated since 2.5.3 (2007) and is
marked as obsolete in grep 3.8, see
https://lists.gnu.org/archive/html/info-gnu/2022-09/msg00001.html

Also remove a stray \ before the # symbol,
which doesn't need escaping in grep.

Prevents the following warnings during the
commit-msg hook:

  egrep: warning: egrep is obsolescent; using grep -E
  egrep: warning: egrep is obsolescent; using grep -E
  egrep: warning: egrep is obsolescent; using grep -E
  grep: warning: stray \ before #
  egrep: warning: egrep is obsolescent; using grep -E

Resolves: #101329
Releases: main, 12.4, 11.5
Change-Id: I2777d8ffd640598d7c92bed166b793b285e5fa06
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/79979


Tested-by: Benjamin Franzke <ben@bnf.dev>
Tested-by: core-ci <typo3@b13.com>
Reviewed-by: Benjamin Franzke <ben@bnf.dev>