test: re-enable test_connect_stdio on Windows

Problem:
test_connect_stdio was marked xfail on Windows since #544, but Neovim
has since fixed stdio channel handling for detached processes on Windows
(neovim/neovim#37977).

Solution:
Remove the xfail mark from test_connect_stdio. Keep xfail on
test_connect_socket since it uses UNIX domain sockets which are
fundamentally unsupported on Windows.

Author: justinmk

test/test_attach.py

@@ -18,8 +18,8 @@
 # pylint: disable=redefined-outer-name
 
 
-xfail_on_windows = pytest.mark.xfail(
-    "os.name == 'nt'", reason="Broken in Windows, see #544")
+_xfail_socket_on_windows = pytest.mark.xfail(
+    "os.name == 'nt'", reason="UNIX sockets not supported on Windows, see #544")
 
 
 @pytest.fixture
@@ -36,7 +36,7 @@ def tmp_socket() -> Generator[str, None, None]:
                 os.unlink(addr)
 
 
-@xfail_on_windows
+@_xfail_socket_on_windows
 def test_connect_socket(tmp_socket: str) -> None:
     """Tests UNIX socket connection."""
     p = subprocess.Popen(["nvim", "--clean", "-n", "--headless",
@@ -91,7 +91,6 @@ def test_connect_tcp_no_server() -> None:
         pynvim.attach('tcp', address='127.0.0.1', port=port)
 
 
-@xfail_on_windows
 def test_connect_stdio(vim: Nvim) -> None:
     """Tests stdio connection, using jobstart(..., {'rpc': v:true})."""