refactor: inline updateClassName utility in module

Author: atomiks

src/className-plugin.js

@@ -1,4 +1,10 @@
-import {updateClassName} from './utils';
+function updateClassName(box, action, classNames) {
+  classNames.split(/\s+/).forEach(name => {
+    if (name) {
+      box.classList[action](name);
+    }
+  });
+}
 
 export const classNamePlugin = {
   name: 'className',

src/utils.js

@@ -16,14 +16,6 @@ export function ssrSafeCreateDiv() {
   return isBrowser && document.createElement('div');
 }
 
-export function updateClassName(box, action, classNames) {
-  classNames.split(/\s+/).forEach(name => {
-    if (name) {
-      box.classList[action](name);
-    }
-  });
-}
-
 export function toDataAttributes(attrs) {
   const dataAttrs = {
     'data-placement': attrs.placement,