Use Node 12 in Playwright job runner.

Author: onurtemizkan

.github/workflows/build.yml

@@ -283,6 +283,9 @@ jobs:
         uses: actions/checkout@v2
       - name: Set up Node
         uses: actions/setup-node@v1
+        with:
+          node-version: '12'
+          fetch-depth: 0
       - name: Check dependency cache
         uses: actions/cache@v2
         with: