fix(ci): quote summary string

Author: jeertmans

.github/workflows/rustbench.yml

@@ -65,6 +65,6 @@ jobs:
       run: |
         echo '### Benchmark results' >> $GITHUB_STEP_SUMMARY
         echo '```' >> $GITHUB_STEP_SUMMARY
-        echo ${{ steps.compare.outputs.results }} >> $GITHUB_STEP_SUMMARY
+        echo '${{ steps.compare.outputs.results }}' >> $GITHUB_STEP_SUMMARY
         echo '```' >> $GITHUB_STEP_SUMMARY
         echo 'EOF' >> $GITHUB_STEP_SUMMARY