fix(responses): end tool search lowering with an explicit return

CodeQL flags the match in _lowered_call_kwargs for mixing explicit returns with a fall through, since it doesn't know assert_never never returns. The exhaustiveness check now follows the match as return assert_never(lowering), as elsewhere in the codebase, which keeps basedpyright clean

litellm/responses/tool_search/handler.py

@@ -43,8 +43,7 @@ def _lowered_call_kwargs(
                 model=model,
                 llm_provider=custom_llm_provider if isinstance(custom_llm_provider, str) else "",
             )
-        case _:
-            assert_never(lowering)
+    return assert_never(lowering)
 
 
 def _lifted(result: object) -> ResponsesAPIResponse | BaseResponsesAPIStreamingIterator: