Fix ray-project/Aviary integration (#6607)

- Description: The aviary integration has changed url link. This PR
provide fix for those changes and also it makes providing the input URL
optional to the API (since they can be set via env variables).
  - Issue: N/A
  - Dependencies: N/A
  - Twitter handle: N/A

---------

Signed-off-by: Kourosh Hakhamaneshi <kourosh@anyscale.com>

tests/integration_tests/llms/test_aviary.py

@@ -5,6 +5,7 @@ from langchain.llms.aviary import Aviary
 
 def test_aviary_call() -> None:
     """Test valid call to Anyscale."""
-    llm = Aviary(model="test/model")
+    llm = Aviary()
     output = llm("Say bar:")
+    print(f"llm answer:\n{output}")
     assert isinstance(output, str)