fix: update submodule before caching

.github/workflows/tests.yml

@@ -23,6 +23,9 @@ jobs:
           python-version: '3.10'
           submodules: true
 
+      - name: Initialize and update submodules
+        run: git submodule update --init --recursive
+
       - name: Load cached Poetry installation
         id: cached-poetry
         uses: actions/cache@v3