scale: Fix a typo

We want to update the label size request when
the adjustment changes, not when anything else
changes.

This may be the reason for crash reports like
https://retrace.fedoraproject.org/faf/problems/bthash/?bth=1e5cc1318358d5db298e5d6c2ec47361922cce74

gtk/gtkscale.c

@@ -311,7 +311,7 @@ gtk_scale_notify (GObject    *object,
 
       g_free (values);
     }
-  else if (strcmp (pspec->name, "adjustment"))
+  else if (strcmp (pspec->name, "adjustment") == 0)
     {
       if (priv->value_widget)
         update_label_request (scale);