community: Replace gmane archive link with a mail-archive one.
community: Replace gmane archive link with a mail-archive one.

The link to gname in the community page[1] seems to be broken:
http://dir.gmane.org/gmane.comp.version-control.git

Gmane itself seems to be down, I don't know if temporarily or not, so after a
quick search I found another archive in mail-archive.com[2], and thought that I
could be worth to replace them.

[1]: https://git-scm.com/community
[2]: https://www.mail-archive.com/git@vger.kernel.org/

git/git-scm.com,jnavila/gitscm-next,jnavila/gitscm-next,jasonlong/git-scm.com,git/git-scm.com,jnavila/gitscm-next,git/git-scm.com,mosoft521/gitscm-next,Mokolea/git-scm.com,mosoft521/gitscm-next,Mokolea/git-scm.com,Mokolea/git-scm.com,mosoft521/gitscm-next,Mokolea/git-scm.com,jasonlong/git-scm.com,jasonlong/git-scm.com,git/git-scm.com,mosoft521/gitscm-next,jasonlong/git-scm.com,jnavila/gitscm-next