gui2/preferences: Use labelless toggle buttons in Advanced

The labels are implemented with a different widget on a separate column,
the the reserved space only serves to make things look weird.

data/gui/window/preferences/06_advanced.cfg

@@ -33,7 +33,7 @@
 
 											[toggle_button]
 												id = "value_toggle"
-												definition = "default"
+												definition = "no_label"
 											[/toggle_button]
 										[/column]