Update element-web.yaml

.github/workflows/element-web.yaml

@@ -10,6 +10,9 @@ on:
         branches: [develop, master]
     repository_dispatch:
         types: [upstream-sdk-notify]
+concurrency:
+    group: ${{ github.workflow }}-${{ github.ref }}-${{ github.event_name }}
+    cancel-in-progress: true
 env:
     # These must be set for fetchdep.sh to get the right branch
     REPOSITORY: ${{ github.repository }}