Fix installing pnpm in github actions

The action is buggy and does not read the "packagerManager" field from the "package.json" despite saying so in its documentation

.github/workflows/build_pull_request.yml

@@ -16,6 +16,7 @@ jobs:
       - uses: pnpm/action-setup@v6
         name: Install pnpm
         with:
+          version: 11.1.2
           cache: true
 
       - name: Install modules