ci: use pnpm exec to install playwright

Using our desired version.

Author: thewtex

.github/workflows/playwright.yml

@@ -175,7 +175,7 @@ jobs:
           cache: pnpm
 
       - name: Install Playwright Browsers
-        run: pnpx playwright install --with-deps
+        run: pnpm exec playwright install --with-deps
 
       - name: pnpm install
         run: pnpm install --frozen-lockfile