Fix paint style for older JOSM

Signed-off-by: Taylor Smock <taylor.smock@kaart.com>

src/resources/styles/standard/mapwithai.mapcss

@@ -10,9 +10,11 @@ meta
 /***************************************************
  * Set .mapwithai for all known MapWithAI datasets *
  ***************************************************/
+@supports (min-josm-version: 15289) {
     settings::show_all {
         label: tr("Show possible MapWithAI objects");
     }
+}
 setting::show_new {
     type: boolean;
     label: tr("New");