remove pooled_projection_dim

pooled_projection_dim is unused and leads to a warning when loaded in diffusers:
The config attributes {'pooled_projection_dim': 768} were passed to QwenImageTransformer2DModel, but are not expected and will be ignored. Please verify your config.json configuration file.

transformer/config.json

@@ -13,6 +13,5 @@
   "num_attention_heads": 24,
   "num_layers": 60,
   "out_channels": 16,
-  "patch_size": 2,
-  "pooled_projection_dim": 768
+  "patch_size": 2
 }