Update Airship projects for gerritbot

The Airship project namespace has changed from "openstack" to "airship"
and Airship projects are no longer prefixed with "airship-" as a result
of the OpenDev migration [0]. This change updates the gerritbot projects
for the Airship IRC channel to reflect changes from the migration.

[0] http://lists.openstack.org/pipermail/openstack-discuss/2019-April/004920.html

Change-Id: I33b0ae38d7f65d74197d9ae29db1ad151b40eca3

gerritbot/channels.yaml

@@ -4,7 +4,7 @@ airshipit:
     - patchset-created
     - change-merged
   projects:
-    - ^openstack/airship-.*
+    - ^airship/.*
   branches:
     - master