Install dependencies for mypy CI check

.github/workflows/mypy.yml

@@ -5,10 +5,14 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v4
+        with:
+          submodules: 'true'
       - name: Setup Python 3.9
         uses: actions/setup-python@v5
         with:
           python-version: 3.9
+          cache: 'pip'
+      - run: python -m pip install -r requirements.txt
       - name: Install mypy
         run: pip install mypy
       - name: Run mypy