ci: add synchronize event and check for beta label using contains()

.github/workflows/beta.yml

@@ -3,11 +3,11 @@ name: beta
 on:
   workflow_dispatch:
   pull_request:
-    types: [labeled]
+    types: [labeled, synchronize]
 
 jobs:
   sync:
-    if: github.event_name == 'workflow_dispatch' || github.event.label.name == 'beta'
+    if: github.event_name == 'workflow_dispatch' || contains(github.event.pull_request.labels.*.name, 'beta')
     runs-on: blacksmith-4vcpu-ubuntu-2404
     permissions:
       contents: write