Actually install playwright in artifact build script now that it's not installed by default

Basically copying bfea348e40

.github/workflows/release-branch-artifact.yaml

@@ -25,6 +25,8 @@ jobs:
         npm test
       env:
         CI: true
+    - name: Adding playwright
+      run: npm install --no-save --no-package-lock playwright   
     - name: Validate the browser can import TypeScript
       run: gulp test-browser-integration
     - name: LKG, clean, and pack