Clean up unused IRC channels

Remove some unused OpenStack IRC channels from our gerritbot config.
Accessbot configuration is being left in place to provide continuity
in case the channel needs to be resurrected at some future date.
These were all discussed in an openstack-discuss ML thread in March,
and nobody has raised any objection:

http://lists.openstack.org/pipermail/openstack-discuss/2020-March/013257.html

A follow-up notification about this change is being sent to the ML
as well.

Change-Id: I8e7e945bea87b4e53883e9679ac149a5cdece9b6

gerritbot/channels.yaml

@@ -35,19 +35,6 @@ cloudkitty:
   branches:
     - master
 
-congress:
-  events:
-    - patchset-created
-    - change-merged
-  projects:
-    - openstack/congress
-    - openstack/congress-dashboard
-    - openstack/congress-specs
-    - openstack/congress-tempest-plugin
-    - openstack/python-congressclient
-  branches:
-    - master
-
 git-upstream:
   events:
     - patchset-created
@@ -86,22 +73,6 @@ midonet:
   branches:
     - master
 
-murano:
-  events:
-    - patchset-created
-    - change-merged
-  projects:
-    - openstack/murano
-    - openstack/murano-agent
-    - openstack/murano-apps
-    - openstack/murano-dashboard
-    - openstack/murano-pkg-check
-    - openstack/murano-specs
-    - openstack/python-muranoclient
-    - x/murano-plugin-networking-sfc
-  branches:
-    - master
-
 opendev:
   events:
     - patchset-created
@@ -363,15 +334,6 @@ openstack-blazar:
   branches:
     - master
 
-openstack-browbeat:
-  events:
-    - patchset-created
-    - change-merged
-  projects:
-    - x/browbeat
-  branches:
-    - master
-
 openstack-charms:
   events:
     - patchset-created
@@ -538,15 +500,6 @@ openstack-dpm:
   branches:
     - master
 
-openstack-dragonflow:
-  events:
-    - patchset-created
-    - change-merged
-  projects:
-    - openstack/dragonflow
-  branches:
-    - master
-
 openstack-ekko:
   events:
     - patchset-created
@@ -669,15 +622,6 @@ openstack-ha:
   branches:
     - master
 
-openstack-heat-translator:
-  events:
-    - patchset-created
-    - change-merged
-  projects:
-    - openstack/heat-translator
-  branches:
-    - master
-
 openstack-helm:
   events:
     - patchset-created
@@ -1037,17 +981,6 @@ openstack-nemesis:
   branches:
     - master
 
-openstack-net-bgpvpn:
-  events:
-    - patchset-created
-    - change-merged
-  projects:
-    - openstack/networking-bgpvpn
-  branches:
-    - master
-    - backport/kilo
-    - backport/juno
-
 openstack-networking-cisco:
   events:
     - patchset-created
@@ -1200,16 +1133,6 @@ openstack-pandaman:
   branches:
     - master
 
-openstack-performance:
-  events:
-    - patchset-created
-    - change-merged
-  projects:
-    - openstack/osprofiler
-    - openstack/performance-docs
-  branches:
-    - master
-
 openstack-placement:
   events:
     - patchset-created