Bump codecov/codecov-action from 2 to 3

Bumps [codecov/codecov-action](https://github.com/codecov/codecov-action) from 2 to 3.
- [Release notes](https://github.com/codecov/codecov-action/releases)
- [Changelog](https://github.com/codecov/codecov-action/blob/master/CHANGELOG.md)
- [Commits](codecov/codecov-action@v2...v3)

---
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/tests.yml

@@ -43,7 +43,7 @@ jobs:
       run: |
         tox -e tests
     - name: Upload coverage to Codecov
-      uses: codecov/codecov-action@v2
+      uses: codecov/codecov-action@v3
       with:
         flags: ${{ matrix.os }}_${{ matrix.python-version }}
         verbose: true