gtestutils: Mention G_DISABLE_ASSERT in documentation for g_test_init()
gtestutils: Mention G_DISABLE_ASSERT in documentation for g_test_init()

g_test_init() bails if G_DISABLE_ASSERT is defined. Mention that. This
is a follow-up to
https://gitlab.gnome.org/GNOME/glib/merge_requests/174.

Signed-off-by: Philip Withnall <withnall@endlessm.com>

https://gitlab.gnome.org/GNOME/glib/issues/1446

endlessm/glib,endlessm/glib,endlessm/glib,endlessm/glib,endlessm/glib