[docs] Fix docstring arguments that don't match the signatures (#14778)

- TransformerSpatioTemporalModel.forward: no num_frames parameter
- get_2d_rotary_pos_embed_lumina: parameters are len_h / len_w, not grid
- AutoencoderKLHunyuanImageRefiner / AutoencoderKLHunyuanVideo15.tiled_decode:
  no return_dict parameter; they return a plain tensor

Co-authored-by: revanth-045 <revanthreddych159@gmail.com>
Co-authored-by: Claude Opus 5 <noreply@anthropic.com>