Fix X11 update_auth chaange to work on Windows

Commit 9e32fd1 worked fine on Linux and macOS, but removing the close of
new_file before doing the file rename caused errors on Windows. This adds
back the explicit file close before calling os.replace() when there's
no error. If there is an error, though, the "with" statement will still
trigger a close.

Author: ronf

asyncssh/x11.py

@@ -503,6 +503,8 @@ async def update_xauth(auth_path: Optional[str], host: str, dpynum: str,
                     entry.dpynum != new_entry.dpynum):
                 new_file.write(bytes(entry))
 
+        new_file.close()
+
         os.replace(new_auth_path, auth_path)