Bump actions/cache from 3.3.2 to 4.0.2 (#359)

.github/workflows/main.yml

@@ -37,7 +37,7 @@ jobs:
           flake8 .
 
       - name: Set up mypy cache
-        uses: actions/cache@v3.3.2
+        uses: actions/cache@v4.0.2
         with:
           path: .mypy_cache
           key: mypy1-${{ hashFiles('./graphqldb/**/*.py') }}-${{ hashFiles('./tests/**/*.py') }}