Add Label definition for PTL-Approved

Currently we're just seeing "Allow" in:

  https://review.opendev.org/#/admin/projects/openstack/releases,access

Maybe it's because there is no definition of the label qualities.

Change-Id: I3e7aba14360e4df2e4d7c8f386d3fb9c8b92fa73

gerrit/acls/openstack/releases.config

@@ -10,3 +10,10 @@ requireContributorAgreement = true
 
 [submit]
 mergeContent = true
+
+[label "PTL-Approved"]
+copyAllScoresOnTrivialRebase = true
+defaultValue = 0
+function = NoOp
+value = 0 Abstain
+value = +1 Approved by PTL