tests: Remove an unnecessary sleep from desktop-app-info test

g_app_info_launch_default_for_uri_async() has already returned by this point, so waiting a little longer is not really going to help. We’re also trying to test a negative, which is never guaranteed, so just save some time and don’t sleep instead.

This speeds the test up by about 5%.

Signed-off-by: Philip Withnall pwithnall@endlessos.org