datalets v0.5.2 — packaging fix + docs refresh

Packaging fix: the scikit-learn requirement was declared >=1.4 but the code needs >=1.6 (validate_data) — installs on sklearn 1.4/1.5 failed at import. If you're on an older scikit-learn, pip install -U scikit-learn datalets.

Also a documentation de-staling pass: six estimators in the compatibility section, all three check_estimator exemptions listed with their shared tuned-threshold cause, sample_weight/class_weight support properly reflected, API signatures and fitted attributes brought current.