fix: update concurrency group expression in e2e workflow

- Updates concurrency group to use github.ref_name for accurate branch/tag
naming
- Ensures proper cancellation of in-progress runs for same workflow/provider
combination

Signed-off-by: Chmouel Boudjnah <chmouel@redhat.com>

Author: chmouel

.github/workflows/e2e.yaml

@@ -34,7 +34,7 @@ jobs:
       (github.event_name == 'pull_request_target' && (github.event.label.name == 'e2e' || contains(github.event.pull_request.labels.*.name, 'e2e')))
 
     concurrency:
-      group: ${{ github.workflow }}-${{ matrix.provider }}-${{ github.event.pull_request.number || github.ref }}
+      group: ${{ github.workflow }}-${{ matrix.provider }}-${{ github.event.pull_request.number || github.ref_name }}
       cancel-in-progress: true
 
     name: e2e tests