CodeCov warning

[Tomas Pytel]

Fix issue with CodeCov:

->  Issue detecting commit SHA. Please run actions/checkout with fetch-depth > 1 or set to 0
    current dir:  /home/runner/work/fastapi-featureflags/fastapi-featureflags
    project root: .
    Yaml not found, that's ok! Learn more at http://docs.codecov.io/docs/codecov-yaml
==> Running gcov in . (disable via -X gcov)
==> Python coveragepy not found
==> Searching for coverage reports in:
    + .
--> No coverage report found.
    Please visit http://docs.codecov.io/docs/supported-languages