[optim] clean apollo (#6645)

* clean apollo code

* update readme

Former-commit-id: 38b8ec4a99189483124b54df9d6bc6b0d318855a

src/llamafactory/extras/packages.py

@@ -49,9 +49,11 @@ def is_fastapi_available():
 def is_galore_available():
     return _is_package_available("galore_torch")
 
+
 def is_apollo_available():
     return _is_package_available("apollo_torch")
 
+
 def is_gradio_available():
     return _is_package_available("gradio")