test(vcr): drop dead 'from respx import MockRouter' imports

These seven test files were on _RESPX_CONFLICTING_FILES, which made the
auto-marker skip them entirely. Inspecting the source shows the only
respx artifact is a top-level 'from respx import MockRouter' that no
test ever uses - no @pytest.mark.respx, no respx_mock fixture, no
respx.mock context manager. The import is dead code left over from a
previous mocking pattern.

Now that apply_vcr_auto_marker_to_items detects respx per-item via the
marker / fixture chain (b637d9f64a), the file-level skip is no longer
needed for these files - they were the reason the OpenAI tests
(test_o3_reasoning_effort, test_streaming_response[o1/o3-mini],
TestOpenAIO1::test_streaming, TestOpenAIChatCompletion::test_web_search,
TestOpenAIO3::test_web_search, etc.) ran live every CI build despite
the cassette cache being healthy.

Co-authored-by: Mateo Wang <mateo-berri@users.noreply.github.com>

tests/llm_translation/test_gpt4o_audio.py

@@ -11,7 +11,6 @@ sys.path.insert(
 
 import httpx
 import pytest
-from respx import MockRouter
 
 import litellm
 from litellm import Choices, Message, ModelResponse

tests/llm_translation/test_nvidia_nim.py

@@ -11,7 +11,6 @@ sys.path.insert(
 
 import httpx
 import pytest
-from respx import MockRouter
 from unittest.mock import patch, MagicMock, AsyncMock
 
 import litellm

tests/llm_translation/test_openai.py

@@ -12,7 +12,6 @@ sys.path.insert(
 
 import httpx
 import pytest
-from respx import MockRouter
 
 import litellm
 from litellm import Choices, Message, ModelResponse

tests/llm_translation/test_openai_o1.py

@@ -11,7 +11,6 @@ sys.path.insert(
 
 import httpx
 import pytest
-from respx import MockRouter
 
 import litellm
 from litellm import Choices, Message, ModelResponse

tests/llm_translation/test_prompt_caching.py

@@ -11,7 +11,6 @@ sys.path.insert(
 
 import httpx
 import pytest
-from respx import MockRouter
 
 import litellm
 from litellm import Choices, Message, ModelResponse

tests/llm_translation/test_xai.py

@@ -11,7 +11,6 @@ sys.path.insert(
 
 import httpx
 import pytest
-from respx import MockRouter
 
 import litellm
 from litellm import Choices, Message, ModelResponse, EmbeddingResponse, Usage

tests/local_testing/test_router.py

@@ -20,7 +20,6 @@ import os
 from collections import defaultdict
 from concurrent.futures import ThreadPoolExecutor
 from unittest.mock import AsyncMock, MagicMock, patch
-from respx import MockRouter
 import httpx
 from dotenv import load_dotenv
 from pydantic import BaseModel