ci: manually install pnpm via npm for renovate

Manually install pnpm via npm for the renovate environment as the pnpm install action does not allow the install
when anothe package is defined as the packageManager in the root package.json

Author: josephperrott

.github/workflows/ng-renovate.yml

@@ -25,9 +25,8 @@ jobs:
     runs-on: ubuntu-24.04
     steps:
       - uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4.2.2
-      - uses: pnpm/action-setup@a7487c7e89a18df4991f7f222e4898a00d66ddda # v4.1.0
-        with:
-          version: 9.15.4
+      - run: npm install --global [email protected]
+        shell: bash
       - run: yarn --cwd .github/ng-renovate install --immutable
         shell: bash