Remove Manipulator.toggleClass (#31842)

It's only used in one place so it makes more sense to remove it for the time being.

js/src/dom/manipulator.js

@@ -72,18 +72,6 @@ const Manipulator = {
       top: element.offsetTop,
       left: element.offsetLeft
     }
-  },
-
-  toggleClass(element, className) {
-    if (!element) {
-      return
-    }
-
-    if (element.classList.contains(className)) {
-      element.classList.remove(className)
-    } else {
-      element.classList.add(className)
-    }
   }
 }