Remove weekly HA meeting

These meetings have not happened for several months due to low
attendance, so acknowledge this rather than misleading people.  Anyone
wishing to raise HA topics can still use #openstack-ha, and in the
future the OpenStack HA sub-community may will be subsumed by the
self-healing SIG.

https://wiki.openstack.org/wiki/Meetings/HATeamMeeting has been
updated accordingly.

Story: 2001435
Task: 19804
Change-Id: I5d8c0d3bd2b23fe1e250cc6c637bdf785f3cadfe

meetings/high-availability-meeting.yaml

@@ -1,15 +0,0 @@
-project:  High Availability Meeting
-meeting_id: ha
-agenda_url: https://wiki.openstack.org/wiki/Meetings/HATeamMeeting
-schedule:
-  - time:       '0900'
-    day:        Wednesday
-    irc:        openstack-meeting-alt
-    frequency:  weekly
-    start_date: 20160111
-chair:  Adam Spiers (aspiers)
-description:  >
-  If you're interested in High Availability within OpenStack,
-  we have a weekly meeting on IRC. Please feel free to add items to the
-  agenda. NOTE: When adding topics please include your IRC name so we know
-  whose topic it is and how to get more info.