feat: replace pytest-vcr by pytest-recording

1. pytest-vcr does not support httpx - which LiteLLM uses for streaming responses.
2. pytest-vcr is no longer maintained, last commit 6 years ago :fist::skin-tone-4:
3. pytest-recording supports modern request libraries (including httpx) and actively maintained

tests/llm_test.py

@@ -2,6 +2,7 @@ import os
 from time import sleep
 from unittest.mock import MagicMock, patch
 
+import litellm
 import pytest
 from pydantic import BaseModel