refactor: update read_doc function to use ellipsis for no-op implementation in test_unknown_argument_raises_validation_error

Author: elbachir-salik

tests/server/mcpserver/test_func_metadata.py

@@ -1302,8 +1302,7 @@ def fn() -> CallToolResult | str | InputRequiredResult: ...  # pragma: no branch
 def test_unknown_argument_raises_validation_error():
     """SDK-defined: a tools/call argument name not on the tool schema fails validation."""
 
-    def read_doc(topic: str = "") -> str:
-        return topic
+    def read_doc(topic: str = "") -> str: ...  # pragma: no branch
 
     meta = func_metadata(read_doc)
     with pytest.raises(ValidationError):