Improve re-usability of cache-pixi-lock.yml (#2343)

Author: VeckoTheGecko

.github/workflows/cache-pixi-lock.yml

@@ -17,6 +17,7 @@ jobs:
       - uses: actions/checkout@v5
         with:
           fetch-depth: 0
+          submodules: recursive
       - name: Get current date
         id: date
         run: echo "date=$(date +'%Y-%m-%d')" >> "$GITHUB_OUTPUT"