Bump codecov/codecov-action from 2 to 4 (#169)

Author: dependabot[bot]

.github/workflows/codecov.yml

@@ -38,4 +38,4 @@ jobs:
         coverage run setup.py test
 
     - name: Upload Coverage to Codecov
-      uses: codecov/codecov-action@v2
+      uses: codecov/codecov-action@v4