Remove broken notification for starlingx

The OpenDev rename missed the stx repos due to the regex, and
feedback by starlingx folks that this is nice - the notifications were
too much noise.

So, remove the broken notifications.

Change-Id: I3757ca85b64b12c90741a8d5075f59ddb65d549f

gerritbot/channels.yaml

@@ -2257,16 +2257,6 @@ solum:
   branches:
     - master
 
-starlingx:
-  events:
-    - patchset-created
-    - change-merged
-  projects:
-    - ^openstack/stx-.*
-  branches:
-    - ^m/.*
-    - ^r/.*
-
 storyboard:
   events:
     - patchset-created