plot_model_cartoon: remove the deprecation shims (two minor releases after #1124)

Scheduled removals introduced by #1124, all currently warning: the `plot_predictive_mean`/`plot_predictive_samples` boolean pair (FutureWarning shim onto `uncertainty=`), the `alpha_predictive` alias for `alpha_uncertainty` on `plot_func_model`/`plot_func_model_n`, the `n_samples` → `n_reps` kwarg alias on both renderers, and the tolerated-but-ignored `hist_histtype` kwarg.

Start by locating plot_model_cartoon and the renderers affected by the deprecation shims from #1124. Remove the boolean, alpha_predictive, n_samples, and ignored hist_histtype compatibility paths listed in the issue. Done means these arguments are no longer accepted or silently ignored and the associated deprecation warnings are gone.

Written by the indexing model from the issue text.