Use poetry 1.2+ dependency notation for deps variants in pyproject.toml

[approxit]

As #1086 introduced unified scripts in task runners, and dependencies syntax are now in poetry 1.2+ format, its a good time to revisit how we can now describe sphinx and goth related dependencies.

goth and sphinx dependencies are related to development environment, there is no need to publish yapapi with unrelated to user metadata noise.

What to do:

• Move goth and sphinx to different dependency groups
• Update CI to relate the changes
• Update docs / readme files to relate the changes