dbnomics-python-client - fix units tests
- some unit tests are broken (they use series that doesn't exists anymore)
- unit tests that uses
pytest-vcr
silently don't use the cassettes (API mocking) when the package is not installed => API is used and in case of changes (series that are not present anymore typically) this is not clear why tests fails - the majority of tests don't use cassettes so they are vulnerable to data changes