[MNT] Reassess the PyYAML and Cython CI workaround

[WilliamJudge94]

Reassess the legacy CI workaround that prebuilds PyYAML==5.4.1 with a Cython < 3.0 build constraint. PyCaret does not directly import PyYAML or Cython; PyYAML is only included through optional extras.

Verify whether the workaround is still necessary with the uv-native workflow, and remove or replace it if CI can install the dependency reliably without it.

Context: #30

[amotl]

Thanks. It looks like those special considerations are no longer required, so let's remove them?

• [MNT] Remove PyYAML and Cython CI workaround #140