RH_and_GitLab_Configuration.adoc: Remove ipv6 section

This doc currently has a section titled 'GitLab ipv6 Issues'. This issue was
resolved on the Red Hat internal network in May by the ticket [1]
and users should no longer need to apply this configuration change.

[1] https://redhat.service-now.com/help?id=rh_ticket&table=incident&sys_id=67a0e84fdbeb2410c0c8464e13961917&view=ess

Remove the ipv6 section.

Closed #39 (closed)

Suggested-by: Brian Masney bmasney@redhat.com
Signed-off-by: Prarit Bhargava prarit@redhat.com