Revert `AutoencoderKLWan`'s `dim_mult` default value back to list (#12640)

Revert dim_mult back to list and fix type annotation

src/diffusers/models/autoencoders/autoencoder_kl_wan.py

@@ -971,7 +971,7 @@ class AutoencoderKLWan(ModelMixin, AutoencoderMixin, ConfigMixin, FromOriginalMo
         base_dim: int = 96,
         decoder_base_dim: Optional[int] = None,
         z_dim: int = 16,
-        dim_mult: Tuple[int, ...] = (1, 2, 4, 4),
+        dim_mult: List[int] = [1, 2, 4, 4],
         num_res_blocks: int = 2,
         attn_scales: List[float] = [],
         temperal_downsample: List[bool] = [False, True, True],