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>

Documentation/MyFirstContribution.txt

@@ -47,7 +47,7 @@ Veteran contributors who are especially interested in helping mentor newcomers
 are present on the list. In order to avoid search indexers, group membership is
 required to view messages; anyone can join and no approval is required.
 
-==== https://webchat.freenode.net/#git-devel[#git-devel] on Freenode
+==== https://web.libera.chat/#git-devel[#git-devel] on Libera Chat
 
 This IRC channel is for conversations between Git contributors. If someone is
 currently online and knows the answer to your question, you can receive help
@@ -827,7 +827,7 @@ either examining recent pull requests where someone has been granted `/allow`
 (https://github.com/gitgitgadget/git/pulls?utf8=%E2%9C%93&q=is%3Apr+is%3Aopen+%22%2Fallow%22[Search:
 is:pr is:open "/allow"]), in which case both the author and the person who
 granted the `/allow` can now `/allow` you, or by inquiring on the
-https://webchat.freenode.net/#git-devel[#git-devel] IRC channel on Freenode
+https://web.libera.chat/#git-devel[#git-devel] IRC channel on Libera Chat
 linking your pull request and asking for someone to `/allow` you.
 
 If the CI fails, you can update your changes with `git rebase -i` and push your