Set Node.js version to 16 in tests workflow

Author: lastlink

.github/workflows/tests.yaml

@@ -92,7 +92,7 @@ jobs:
           retention-days: ${{ env.retention_days }}
       - uses: actions/setup-node@v6
         with:
-          node-version: current
+          node-version: 16
       - run: npm ci
       - run: npm test
       - name: upload junit
@@ -138,4 +138,4 @@ jobs:
         with:
           token: ${{ secrets.GITHUB_TOKEN }}
           merge-method: squash
-          pull-request-number: ${{ github.event.pull_request.number }}
+          pull-request-number: ${{ github.event.pull_request.number }}