Fix warnings with old glib
diff --git a/test/hb-test.h b/test/hb-test.h
index de9a79a..f36d53b 100644
--- a/test/hb-test.h
+++ b/test/hb-test.h
@@ -152,8 +152,7 @@
 #else
 typedef void (*hb_test_func_t)         (void);
 typedef void (*hb_test_data_func_t)    (gconstpointer user_data);
-typedef void (*hb_test_fixture_func_t) (gpointer      fixture,
-                                        gconstpointer user_data);
+typedef void (*hb_test_fixture_func_t) (void);
 #endif
 
 #if !GLIB_CHECK_VERSION(2,30,0)