fix(ci): use pnpm exec for playwright install

npx doesn't reliably find binaries with pnpm. Since playwright is
already a devDependency, use pnpm exec to run the installed version.

Author: matthew-dean

.github/workflows/ci.yml

@@ -40,8 +40,7 @@ jobs:
         run: pnpm install
       - name: Print put node & npm version
         run: node --version && pnpm --version 
-      # Pin the version of Playwright to match package.json to avoid installing a newer version which may expect different binaries
       - name: Install chromium
-        run: npx playwright@1.50.1 install chromium
+        run: pnpm exec playwright install chromium
       - name: Run unit test
         run: pnpm run test