workflow: upgrade node version

Author: Sascha Goldhofer

.github/workflows/ci.yaml

@@ -14,7 +14,7 @@ jobs:
             - uses: actions/checkout@v3
             - uses: actions/setup-node@v3
               with:
-                  node-version: "16"
+                  node-version: "21"
                   cache: "yarn"
             - name: Install dependencies
               run: yarn --frozen-lockfile