[Protected Files] Revert "Allow 'dependabot[bot]' to edit protected f…

…iles" (#31386)

- Unintentionally allowed anyone with write access to approve and merge dependabot PRs

.github/workflows/protected-files.yaml

@@ -4,7 +4,7 @@ on: pull_request
 
 env:
   # Users allowed to edit protected files without failing check
-  user-allowed: ${{ github.event.pull_request.user.login == 'azure-sdk' || github.event.pull_request.user.login == 'dependabot[bot]' }}
+  user-allowed: ${{ github.event.pull_request.user.login == 'azure-sdk' }}
 
 jobs:
   protected-files: