Move all-sides warp background update code to logic functions

Otherwise it'll go by really fast and rapidly pulsate. To the point
where it seems like it would be an epilepsy trigger, although I
wouldn't know anything about epilepsy other than that it's bad.

desktop_version/src/editor.cpp

@@ -3618,6 +3618,10 @@ void editorlogic()
             graphics.rcol=ed.getwarpbackground(ed.levx, ed.levy);
             graphics.updatebackground(4);
             break;
+        case 3:
+            graphics.rcol=ed.getwarpbackground(ed.levx, ed.levy);
+            graphics.updatebackground(5);
+            break;
         default:
             break;
         }