Add Heat to common-bump-milestone job

Update the list of projects in the common-bump-milestone job parameters:

- Add Heat. Should hopefully allow us (once seeded) to generate
  properly-versioned artefacts from heat-tarball job.

- Remove Python client projects and Melange, which do not use this job
  anymore.

Change-Id: I9dfa7c793a55385bb496823d0285c8f721d1eed7
Reviewed-on: https://review.openstack.org/18323
Reviewed-by: Monty Taylor <mordred@inaugust.com>
Approved: Jeremy Stanley <fungi@yuggoth.org>
Reviewed-by: Jeremy Stanley <fungi@yuggoth.org>
Tested-by: Jenkins

modules/openstack_project/files/jenkins_job_builder/config/release.yaml

@@ -20,17 +20,9 @@
             - keystone
             - horizon
             - quantum
-            - melange
             - cinder
             - ceilometer
-            - python-ceilometerclient
-            - python-cinderclient
-            - python-novaclient
-            - python-openstackclient
-            - python-glanceclient
-            - python-keystoneclient
-            - python-quantumclient
-            - python-swiftclient
+            - heat
       - choice:
           name: BRANCH
           description: The branch to update.