fix: use corepack to install pnpm

Author: oxlumi

.github/workflows/sync-authors-on-pr.yml

@@ -28,10 +28,11 @@ jobs:
           node-version: '22.18.0'
           cache: 'pnpm'
 
-      - name: Setup PNPM
-        uses: pnpm/action-setup@v4
-        with:
-          version: 10.11.0
+      - name: Setup pnpm via corepack
+        run: |
+          corepack enable
+          corepack prepare pnpm@10.11.0 --activate
+          pnpm -v
 
       - name: Install deps
         run: pnpm install --frozen-lockfile