ci: Add two extra gatekeeper triggers

We hit a case that gatekeeper was failing due to thinking the WIP check
had failed, but since it ran the PR had been edited to remove that from
the title. We should listen to edits and unlabels of the PR to ensure that
gatekeeper doesn't get outdated in situations like this.

Signed-off-by: stevenhorsman <steven@uk.ibm.com>

.github/workflows/gatekeeper.yaml

@@ -10,7 +10,9 @@ on:
       - opened
       - synchronize
       - reopened
+      - edited
       - labeled
+      - unlabeled
 
 permissions: {}