workflows/gatekeeper: configure concurrency properly

This will allow to cancel-in-progress the gatekeeper jobs.

Signed-off-by: Wainer dos Santos Moschetta <wainersm@redhat.com>

.github/workflows/gatekeeper-skipper.yaml

@@ -31,7 +31,6 @@ on:
       skip_static:
         value: ${{ jobs.skipper.outputs.skip_static }}
 
-
 jobs:
   skipper:
     runs-on: ubuntu-latest

.github/workflows/gatekeeper.yaml

@@ -12,6 +12,10 @@ on:
       - reopened
       - labeled
 
+concurrency:
+  group: ${{ github.workflow }}-${{ github.event.pull_request.number || github.ref }}
+  cancel-in-progress: true
+
 jobs:
   gatekeeper:
     runs-on: ubuntu-latest