Bump pnpm/action-setup from 5 to 6

Dependabot couldn't find the original pull request head commit, 61b7c36.

Author: dependabot[bot]

.github/workflows/main.yml

@@ -23,7 +23,7 @@ jobs:
       - name: Checkout repo
         uses: actions/checkout@v6
 
-      - uses: pnpm/action-setup@v5
+      - uses: pnpm/action-setup@v6
 
       - name: Set-up Node.js ${{ matrix.node }}
         uses: actions/setup-node@v6