fix(ci): remove hardcoded pnpm version from action-setup

Let pnpm/action-setup infer version from packageManager field.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: timhanlon

.github/workflows/ci.yml

@@ -17,8 +17,6 @@ jobs:
 
       - name: Setup pnpm
         uses: pnpm/action-setup@v4
-        with:
-          version: 10
 
       - name: Setup Node.js
         uses: actions/setup-node@v4