Workaround for GitHub / CodeQL bug

Sometimes GitHub Actions uses bare branch name whereas CodeQL always expects ref.
See https://github.com/github/codeql-action/issues/796

PiperOrigin-RevId: 549548061
diff --git a/.github/workflows/codeql.yml b/.github/workflows/codeql.yml
index fad20e2..e00adf7 100644
--- a/.github/workflows/codeql.yml
+++ b/.github/workflows/codeql.yml
@@ -68,3 +68,5 @@
       uses: github/codeql-action/analyze@v2
       with:
         category: "/language:${{matrix.language}}"
+        ref: "${{ github.ref != 'master' && github.ref || '/refs/heads/master' }}"
+        sha: "${{ github.sha }}"