Remove setuptools and wheel pin once upgrading to gym>0.21.0

[AdamGleave]

We are pinning setuptools and wheel in ci/build_and_activate_venv.ps1 and setuptools in docs/requirements.txt / readthedocs.yml in order to avoid the issue described in https://github.com/freqtrade/freqtrade/issues/8376

This issue should be resolved in recent versions of Gym(nasium), so we should be able to remove this once the next SB3 stable release is made that moves to Gymnasium.