Updated recommended Vcs-Git URL in policy.pod

[Russ Allbery]

I took the liberty of updating the recommended Vcs-Git URL in policy.pod
to change git.debian.org to anonscm.debian.org.  My understanding is that
the actual anonymous public Git service is now on the latter host, and
git.debian.org only continues to support this via port forwarding.

This was caught by Lintian in a new package created with dh-make-perl.  I
also filed a corresponding bug against dh-make-perl for --pkg-perl mode.

-- 
Russ Allbery (rra at debian.org)               <http://www.eyrie.org/~eagle/>