Correct `sample_size` of Stable Diffusion 2's unet to have correct width and height default

unet/config.json

@@ -35,7 +35,7 @@
   "num_class_embeds": null,
   "only_cross_attention": false,
   "out_channels": 4,
-  "sample_size": 64,
+  "sample_size": 96,
   "up_block_types": [
     "UpBlock2D",
     "CrossAttnUpBlock2D",