fix(ci): use pnpm exec for playwright install to match lockfile version

`pnpm dlx playwright install` pulls the latest playwright CLI, which
may download a different chromium revision than the one expected by the
project's locked playwright version. This caused browser-related rstest
examples to fail when the latest playwright (chromium v1217) diverged
from the locked playwright@1.58.1 (chromium v1208).

Switch to `pnpm exec playwright install --with-deps chromium` so the
project's own playwright binary is used to download the matching browser.

Amp-Thread-ID: https://ampcode.com/threads/T-019d4701-dfdb-73c6-a876-29ab299f63cf
Co-authored-by: Amp <amp@ampcode.com>

Author: fi3ework

.github/workflows/ci.yaml

@@ -32,7 +32,7 @@ jobs:
         run: pnpm install
 
       - name: Install Playwright browsers
-        run: pnpm dlx playwright install chromium
+        run: pnpm exec playwright install --with-deps chromium
 
       - name: Build Rspack
         run: |