Remove rubick and milk-dev from gerritbot

These two channels are not setup properly, openstackinfra has no access
to them, milk-dev is not even a registered channel.
The projects are also dead, there has not been any change for them for
several months (last merge in rubick: 2014-06-18, milk: 2014-03-13).

Thus, remove the channels from gerritbot.

Change-Id: I848e36c24797518805cf1e5492a7fec8111cc690

gerritbot/channels.yaml

@@ -118,16 +118,6 @@ magnetodb:
     branches:
       - master
 
-milk-dev:
-    events:
-      - patchset-created
-      - change-merged
-      - x-vrif-minus-2
-    projects:
-      - stackforge/milk
-    branches:
-      - master
-
 murano:
     events:
       - patchset-created
@@ -1065,16 +1055,6 @@ refstack:
     branches:
       - master
 
-rubick:
-    events:
-      - patchset-created
-      - change-merged
-      - x-vrif-minus-2
-    projects:
-      - stackforge/rubick
-    branches:
-      - master
-
 solum:
     events:
       - patchset-created