fix: add pragma no cover to unreachable success path in error test

Author: dgenio

tests/server/fastmcp/test_tool_manager.py

@@ -1034,7 +1034,7 @@ async def failing_tool(should_fail: bool) -> str:
             """A tool that raises an error."""
             if should_fail:
                 raise ValueError("Tool failed intentionally")
-            return "success"
+            return "success"  # pragma: no cover
 
         manager = ToolManager(timeout_seconds=1.0)
         manager.add_tool(failing_tool)