Update build-RTR-NetztestCLI-linux-x64.yml add mandatory tag

Author: dzlabing

.github/workflows/build-RTR-NetztestCLI-linux-x64.yml

@@ -40,5 +40,6 @@ jobs:
         retention-days: 90
     - name: Release
       uses: softprops/action-gh-release@v2
+      if: github.ref_type == 'tag'
       with:
         files: RMBTClient/build/RTR-Netztest/*