image_processor.py: Fixed an error in ValueError's message (#8447)

* image_processor.py: Fixed an error in ValueError's message , as the string's join method tried to join types, instead of strings

Bug that occurred:

f"Input is in incorrect format. Currently, we only support {', '.join(supported_formats)}"
TypeError: sequence item 0: expected str instance, type found

* Fixed: C417 Unnecessary `map` usage (rewrite using a generator expression)

---------
Co-authored-by: Sayak Paul <spsayakpaul@gmail.com>

src/diffusers/image_processor.py

@@ -533,7 +533,7 @@ class VaeImageProcessor(ConfigMixin):
 
         if not is_valid_image_imagelist(image):
             raise ValueError(
-                f"Input is in incorrect format. Currently, we only support {', '.join(supported_formats)}"
+                f"Input is in incorrect format. Currently, we only support {', '.join(str(x) for x in supported_formats)}"
             )
         if not isinstance(image, list):
             image = [image]