Update ci-bdnbenchmark.yml (#890)

.github/workflows/ci-bdnbenchmark.yml

@@ -76,6 +76,7 @@ jobs:
 
       # Run `github-action-benchmark` action for the Continuous Benchmarking Charts (https://microsoft.github.io/garnet/charts/)
       - name: Store benchmark result for charts
+        if: github.ref == 'refs/heads/main'
         uses: benchmark-action/github-action-benchmark@v1
         with:
           name: ${{matrix.test}} (${{matrix.os}}  ${{matrix.framework}} ${{matrix.configuration}})
@@ -87,4 +88,4 @@ jobs:
           benchmark-data-dir-path: 'website/static/charts'
           auto-push: true
           max-items-in-chart: 50
-
+