commit-template: remove outdated notice about explicit paths

commit-template: remove outdated notice about explicit paths

The notice that "git commit <paths>" default to "git commit
--only <paths>" was there since 756e3ee0 ("Merge branch
'jc/commit'", 2006-02-14).  Back then, existing users of Git
expected the command doing "git commit --include <paths>", and
after the behaviour of the command was changed to align with
other people's "$scm commit <paths>", the text was added to help
them transition their expectations.

Remove the message that now has outlived its usefulness.

Signed-off-by: Kaartic Sivaraam <kaarticsivaraam91196@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>