test: use older node (for gatsby v3)

Author: pieh

.github/workflows/test.yml

@@ -14,7 +14,7 @@ jobs:
       - uses: actions/checkout@v3
       - uses: actions/setup-node@v3
         with:
-          node-version: '*'
+          node-version: '18'
       - name: Global Node packages cache
         uses: actions/cache@v3
         with: