Maintenance PR

[irfan-dahir]

This PR resolves/changes

• [x] https://github.com/jikan-me/jikan/issues/447

  • no decoupling is needed via code. We instead remove JikanTest class which was making duplicate calls via API methods. We're already testing for those calls in the Parser tests.

• [x] Fixtures have been submitted as PR to https://github.com/jikan-me/jikan-fixtures/pull/4

  • Will be merged there once this PR is merged.

• [x] Updates tests

• [x] ⚠Review Tests (still broken - will be fixed once https://github.com/jikan-me/jikan/pull/476 is merged)