fix: remove the deployed storybook when the PR is closed (#13)

# Description

Disable the Feature Branch workflow to run when a PR is closed.

## Reason

Save minutes in CI runs, since there's no actions to be done in this
workflow.

---

<!-- Auto-generated section. DO NOT DELETE -->

.github/workflows/on-pull-request.yml

@@ -6,7 +6,6 @@ on:
       - opened
       - reopened
       - synchronize
-      - closed
 
 concurrency: preview-${{ github.ref }}