Remove some unused parameter in CrossAttnUpBlock2D (#1034)

Remove some unused parameter

The `downsample_padding` parameter does not seem to be used in `CrossAttnUpBlock2D` (or by any up block for that matter) so removing it.

src/diffusers/models/unet_2d_blocks.py

@@ -1053,7 +1053,6 @@ class CrossAttnUpBlock2D(nn.Module):
         cross_attention_dim=1280,
         attention_type="default",
         output_scale_factor=1.0,
-        downsample_padding=1,
         add_upsample=True,
     ):
         super().__init__()