enable size-check for manual runs

Author: lobsterkatie

.github/workflows/build.yml

@@ -123,8 +123,8 @@ jobs:
           key: ${{ env.BUILD_CACHE_KEY }}
       - name: Check bundle sizes
         uses: getsentry/size-limit-action@v3
-        # Only run size check on master or pull requests
-        if: github.ref == 'refs/heads/master' || github.event_name == 'pull_request'
+        # Don't run size check on release branches - at that point, we're already committed
+        if: ${{ !startsWith(github.ref, 'release') }}
         with:
           github_token: ${{ secrets.GITHUB_TOKEN }}
           # see https://github.com/getsentry/size-limit-action#usage