fix(ci): remove pnpm cache parameter before corepack enable

The baseline allowlist workflow was failing with:
  ##[error]Unable to locate executable file: pnpm

Root cause: setup-node with cache: 'pnpm' runs before corepack enable,
but pnpm isn't available until after corepack enable runs.

Fix: Remove cache: 'pnpm' from both jobs (gen-matrix and run-allowlisted).
The workflow will manually install dependencies via corepack + pnpm.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <[email protected]>

Author: mirqtio

.github/workflows/playwright-baseline-allowlist.yml

@@ -23,7 +23,6 @@ jobs:
       - uses: actions/setup-node@v4
         with:
           node-version: '22.x' # Match local Node v22.15.0
-          cache: 'pnpm'
 
       - name: Install deps
         run: |
@@ -49,7 +48,6 @@ jobs:
       - uses: actions/setup-node@v4
         with:
           node-version: '22.x' # Match local Node v22.15.0
-          cache: 'pnpm'
 
       - name: Install browsers (Playwright)
         run: |