ci(.github): skip Playwright apt installation (#28292)

Playwright's `--with-deps` flag performs a live apt refresh and install
in the E2E and Storybook jobs, even though the runner images already
contain the required system libraries.

Install only Playwright's pinned Chromium build in CI so apt mirror
failures cannot block browser setup.

Closes DEVEX-792

.github/workflows/ci.yaml

@@ -1004,7 +1004,7 @@ jobs:
       - run: make site/e2e/bin/coder
         name: make coder
 
-      - run: pnpm playwright:install
+      - run: pnpm exec playwright install chromium
         working-directory: site
 
       # Cache the Coder release binaries downloaded by the outdatedCLI /
@@ -1100,7 +1100,7 @@ jobs:
         working-directory: site/
         name: Build Storybook
 
-      - run: pnpm playwright:install
+      - run: pnpm exec playwright install chromium
         working-directory: site/
         name: Install Chromium