fixed modulation bug

Author: ChrisLiu6

src/diffusers/utils/import_utils.py

@@ -230,7 +230,6 @@ def _is_package_available(pkg_name: str, get_dist_name: bool = False) -> Tuple[b
 _aiter_available, _aiter_version = _is_package_available("aiter")
 _kornia_available, _kornia_version = _is_package_available("kornia")
 _nvidia_modelopt_available, _nvidia_modelopt_version = _is_package_available("modelopt", get_dist_name=True)
-_apex_available, _apex_version = _is_package_available("apex")
 
 
 def is_torch_available():
@@ -421,10 +420,6 @@ def is_kornia_available():
     return _kornia_available
 
 
-def is_apex_available():
-    return _apex_available
-
-
 # docstyle-ignore
 FLAX_IMPORT_ERROR = """
 {0} requires the FLAX library but it was not found in your environment. Checkout the instructions on the