memory: tests: Fix test to ensure all logs are less severe than WARN

If GST_DEBUG is enabled the existing test will fail as it gets INFO
log messages.

Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/9273>

subprojects/gstreamer/tests/check/gst/gstmemory.c

@@ -679,8 +679,7 @@ _custom_log_func (GstDebugCategory * category,
     GstDebugLevel level, const gchar * file, const gchar * function,
     gint line, GObject * object, GstDebugMessage * message, gpointer unused)
 {
-  const gchar *dbg_msg = gst_debug_message_get (message);
-  fail_unless (dbg_msg == NULL);
+  ck_assert_uint_gt (level, GST_LEVEL_WARNING);
 }
 
 #ifndef GST_DISABLE_GST_DEBUG