Update doc build job to deploy only if ref is main (#2386)

Summary: Pull Request resolved: #2386

Reviewed By: PaulZhang12

Differential Revision: D62586537

Pulled By: iamzainhuda

fbshipit-source-id: ce8f2229872e9a21950552af5c54f230fa8c67e6

.github/workflows/docs.yml

@@ -88,6 +88,7 @@ jobs:
     - name: Get output time
       run: echo "The time was ${{ steps.build.outputs.time }}"
     - name: Deploy
+      if: github.ref == 'refs/heads/main'
       uses: JamesIves/github-pages-deploy-action@releases/v3
       with:
           ACCESS_TOKEN: ${{ secrets.GITHUB_TOKEN }}