docs: remove unused mentoring mailing list reference

The git-mentoring group was initially created to help newcomers
with their development itches. However, in practice,
most of their questions were already being addressed
directly on the mailing list, and contributors consistently
received helpful responses there.

Remove the mentoring group details from the Documentation.

Signed-off-by: K Jayatheerth <jayatheerthkulkarni2005@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Author: jayatheerthkulkarni

Documentation/MyFirstContribution.adoc

@@ -40,14 +40,6 @@ the list by sending an email to <git+subscribe@vger.kernel.org>
 The https://lore.kernel.org/git[archive] of this mailing list is
 available to view in a browser.
 
-==== https://groups.google.com/forum/#!forum/git-mentoring[git-mentoring@googlegroups.com]
-
-This mailing list is targeted to new contributors and was created as a place to
-post questions and receive answers outside of the public eye of the main list.
-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://web.libera.chat/#git-devel[#git-devel] on Libera Chat
 
 This IRC channel is for conversations between Git contributors. If someone is