ci: rely on package.json packageManager for pnpm version

Author: justin-schroeder

.github/workflows/main.yml

@@ -18,8 +18,7 @@ jobs:
         uses: actions/checkout@v4
       - name: Setup pnpm
         uses: pnpm/action-setup@v4
-        with:
-          version: 10
+        # version is read from package.json#packageManager
       - name: Setup Node.js
         uses: actions/setup-node@v4
         with: