fix dummy import for AudioLDM2 (#4741)

* fix import

* style

src/diffusers/pipelines/audioldm2/__init__.py

@@ -11,8 +11,9 @@ try:
         raise OptionalDependencyNotAvailable()
 except OptionalDependencyNotAvailable:
     from ...utils.dummy_torch_and_transformers_objects import (
+        AudioLDM2Pipeline,
         AudioLDM2ProjectionModel,
-        AudioLDMPipeline,
+        AudioLDM2UNet2DConditionModel,
     )
 else:
     from .modeling_audioldm2 import AudioLDM2ProjectionModel, AudioLDM2UNet2DConditionModel