chore: Remove dependency caching on GHA

[DLesage25]

Note

Removes Poetry/venv caching from CI and always installs dependencies during SDK tests and in the reusable setup action.

• CI/GitHub Actions:
  • all-sdk-tests.yml:
    • Removed venv caching (actions/cache) and the conditional install; always runs poetry install and NLTK download in a single "Install dependencies" step.
    • Retains Poetry setup and poetry env use with matrix Python versions.
  • actions/setup-python-env/action.yml:
    • Dropped cache: 'poetry' from actions/setup-python@v4 configuration.

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