Bump codecov/codecov-action from v1.0.10 to v1.2.1 (#909)

Bumps [codecov/codecov-action](https://github.com/codecov/codecov-action) from v1.0.10 to v1.2.1.
- [Release notes](https://github.com/codecov/codecov-action/releases)
- [Changelog](https://github.com/codecov/codecov-action/blob/master/CHANGELOG.md)
- [Commits](codecov/codecov-action@v1.0.10...e156083)

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

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

.github/workflows/ci_tests.yaml

@@ -137,7 +137,7 @@ jobs:
 
       # Upload coverage to Codecov
       - name: Upload coverage to Codecov
-        uses: codecov/codecov-action@v1.0.10
+        uses: codecov/codecov-action@v1.2.1
         with:
           file: ./coverage.xml # optional
           env_vars: OS,PYTHON