CI: Disable metal3-integration test job

The metal3-integration CI job is not smart enough to know which
branches to pull for it to correctly test the branch, and so it
should be disabled on this branch.

Change-Id: If04a5b97722cc1a8e125c3348e09339c3a7ce0eb
(cherry picked from commit 4cb0af7fd6)

zuul.d/project.yaml

@@ -47,7 +47,10 @@
         # NOTE(rpittau): Currently broken because of an issue with parted
         - metalsmith-integration-glance-centos9-legacy:
             voting: false
-        - metal3-integration
+        # NOTE(TheJulia): At present, metal3 doesn't leverage
+        # stable branches, and as far as we are aware these jobs
+        # can be removed once this branch is made stable.
+        # - metal3-integration
         # Non-voting jobs
         - ironic-inspector-tempest:
             voting: false
@@ -97,7 +100,10 @@
         - ironic-tempest-ipa-partition-uefi-pxe-grub2
         # NOTE(rpittau): Currently broken because of an issue with parted
         #- metalsmith-integration-glance-centos9-legacy
-        - metal3-integration
+        # NOTE(TheJulia): At present, metal3 doesn't leverage
+        # stable branches, and as far as we are aware these jobs
+        # can be removed once this branch is made stable.
+        # - metal3-integration
     experimental:
       jobs:
         # TODO(dtantsur): these jobs are useful but currently hopelessly