ci: use pnpm v9

.github/workflows/ci.yml

@@ -36,7 +36,7 @@ jobs:
     - name: Install pnpm
       uses: pnpm/action-setup@v2.4.0
       with:
-        version: next-8
+        version: next-9
         standalone: true
     - name: Setup Node
       uses: actions/setup-node@v3

.github/workflows/release.yml

@@ -31,7 +31,7 @@ jobs:
       - name: Install pnpm
         uses: pnpm/action-setup@v2.4.0
         with:
-          version: latest-8
+          version: next-9
           standalone: true
       - name: pnpm install
         # We use --force because we want all artifacts of @reflink/reflink to be installed.