fix update-node-modules-cache workflow (facebook#45547)

Summary:
Pull Request resolved: facebook#45547

Was missing the step to checkout the repo before running yarn.

Changelog: [Internal]

Reviewed By: sammy-SC, realsoelynn

Differential Revision: D59979543

fbshipit-source-id: 2ab52efbc655cb6ff7b6544ff3939c019c5d45a6

.github/workflows/update-node-modules-cache.yml

@@ -10,6 +10,8 @@ jobs:
   update_node_modules_cache:
     runs-on: ubuntu-latest
     steps:
+      - name: Checkout
+        uses: actions/checkout@v4
       - name: Install yarn dependencies and update cache
         uses: ./.github/actions/yarn-install-with-cache
         with: