Revert to node 14 until we update the base image

Author: s1hofmann

.github/workflows/snapshot_release.yaml

@@ -45,7 +45,7 @@ jobs:
             npm test
       - name: Run Docker E2E tests
         if: ${{matrix.os == 'ubuntu-latest'}}
-        run: docker exec nut-ci bash -c "bash $PWD/.build/build.sh ${PWD} ${{matrix.node}}"
+        run: docker exec nut-ci bash -c "bash $PWD/.build/build.sh ${PWD} 14"
       - name: Run Electron e2e test subpackage
         uses: GabrielBB/xvfb-action@v1
         with: