ci: simplify storybook workflow concurrency key

Agent-Logs-Url: https://github.com/objectstack-ai/objectui/sessions/9e1dd432-975f-44ae-9cfe-adbf9e66eb15

Co-authored-by: hotlong <50353452+hotlong@users.noreply.github.com>

Author: Copilot

.github/workflows/storybook-tests.yml

@@ -8,7 +8,7 @@ on:
       - "pnpm-lock.yaml"
 
 concurrency:
-  group: storybook-tests-${{ github.event.pull_request.number || github.ref }}
+  group: storybook-tests-${{ github.ref }}
   cancel-in-progress: true
 
 permissions: