Fix CI: let pnpm/action-setup read packageManager from package.json

Specifying both `version: 10` in the action and `packageManager` in
package.json triggers ERR_PNPM_BAD_PM_VERSION. Keep package.json as
the single source of truth.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

Author: l-media

.github/workflows/ci.yml

@@ -21,7 +21,6 @@ jobs:
       - name: Install pnpm
         uses: pnpm/action-setup@v4
         with:
-          version: 10
           run_install: false
 
       - name: Setup Node.js ${{ matrix.node }}