tests: Increase a timeout in contexts test
The timeout is just to stop the test hanging forever, so there’s no need for it to be so short. It’s caused at least one spurious CI failure: https://gitlab.gnome.org/GNOME/glib/-/jobs/2445023.
Signed-off-by: Philip Withnall pwithnall@endlessos.org
Fixes: #2837 (closed)
Closes #2837 (closed)