fix: add trailing newline to _exception_utils.py

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: g97iulio1609

src/mcp/shared/_exception_utils.py

@@ -83,4 +83,4 @@ async def open_task_group() -> AsyncIterator[anyio.abc.TaskGroup]:
         collapsed = collapse_exception_group(eg, cancelled_type=cancelled_cls)
         if collapsed is not eg:
             raise collapsed from eg
-        raise  # pragma: lax no cover
+        raise  # pragma: lax no cover