[ci-change] remove upload stable artifacts

**Phenomenon and reproduction steps**

none

**Root cause and solution**

none

**Impactions**

none

**Test method**

none

**Affected branch(es)**

- v6.1

**Checklist**

- [ ] Dependencies update required
- [ ] Common bug (similar problem in other repo)

.github/workflows/main.yml

@@ -185,8 +185,3 @@ jobs:
         run: |
           cd release
           ossutil cp -rf deepflow-gui-grafana.tar.gz  oss://deepflow-ce/pkg/grafana-plugin/${{ env.IMAGE_TAG_PREFIX }}/deepflow-gui-grafana.tar.gz
-      - name: upload stable artifacts
-        if: "startsWith(github.ref, 'refs/tags/')"
-        run: |
-          cd release
-          ossutil cp -rf deepflow-gui-grafana.tar.gz oss://deepflow-ce/pkg/grafana-plugin/stable/deepflow-gui-grafana.tar.gz