test: ignore coverage branch arc on 3.14

Author: Jianke LIN

tests/server/test_stdio.py

@@ -246,7 +246,7 @@ async def handle_call_tool(ctx: ServerRequestContext, params: CallToolRequestPar
         write_stream,
     ):
         with anyio.fail_after(5):
-            async with anyio.create_task_group() as tg:
+            async with anyio.create_task_group() as tg:  # pragma: no branch
                 tg.start_soon(server.run, read_stream, write_stream, server.create_initialization_options())
                 await both_tools_started.wait()
                 allow_tools_to_finish.set()