Bump codecov/codecov-action from 3 to 4

Bumps [codecov/codecov-action](https://github.com/codecov/codecov-action) from 3 to 4.
- [Release notes](https://github.com/codecov/codecov-action/releases)
- [Changelog](https://github.com/codecov/codecov-action/blob/main/CHANGELOG.md)
- [Commits](codecov/codecov-action@v3...v4)

---
updated-dependencies:
- dependency-name: codecov/codecov-action
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <[email protected]>

.github/workflows/ci_tests.yml

@@ -106,14 +106,14 @@ jobs:
 
     - name: Upload coverage to Codecov
       if: matrix.python-version == 3.9
-      uses: codecov/codecov-action@v3
+      uses: codecov/codecov-action@v4
       with:
         flags: aiida
         file: ./coverage.xml
 
     - name: Upload coverage to Codecov
       if: matrix.python-version == 3.9
-      uses: codecov/codecov-action@v3
+      uses: codecov/codecov-action@v4
       with:
         flags: mongo
         file: ./mongo_cov.xml