MyFirstContribution: link #git-devel to Libera Chat

MyFirstContribution: link #git-devel to Libera Chat

Many of the regulars on #git-devel are now on Libera Chat, to the extent
that the community page now lists it as the IRC Channel[1]. This will
help new contributors find the right place, if they choose to ask
questions on `#git-devel`.

Relevant discussion on the IRC transition:
https://lore.kernel.org/git/CAJoAoZ=e62sceNpcR5L5zjsj177uczTnXjcAg+BbOoOkeH8vXQ@mail.gmail.com/

[1] https://git-scm.com/community

Signed-off-by: Atharva Raykar <raykar.ath@gmail.com>
Reviewed-by: Emily Shaffer <emilyshaffer@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>