ENGCOM-1798: [BACKPORT 2.1 #15695] Fixed a couple of typos #15716

 - Merge Pull Request #15716 from dverkade/magento2:2.1-Fix-typos
 - Merged commits:
   1. e0544c2

Author: magento-engcom-team

app/code/Magento/Sales/Block/Adminhtml/Order/Create/Sidebar/AbstractSidebar.php

@@ -69,7 +69,7 @@ public function canDisplay()
     }
 
     /**
-     * Retrieve disply item qty availablity
+     * Retrieve display item qty availability
      *
      * @return false
      */

app/code/Magento/Ui/view/base/web/js/form/components/fieldset.js

@@ -109,14 +109,14 @@ define([
          * @returns {Group} Chainable.
          */
         _setClasses: function () {
-            var addtional = this.additionalClasses,
+            var additional = this.additionalClasses,
                 classes;
 
-            if (_.isString(addtional)) {
-                addtional = this.additionalClasses.split(' ');
+            if (_.isString(additional)) {
+                additional = this.additionalClasses.split(' ');
                 classes = this.additionalClasses = {};
 
-                addtional.forEach(function (name) {
+                additional.forEach(function (name) {
                     classes[name] = true;
                 }, this);
             }

app/code/Magento/Ui/view/base/web/js/form/components/group.js

@@ -54,14 +54,14 @@ define([
          * @returns {Group} Chainable.
          */
         _setClasses: function () {
-            var addtional = this.additionalClasses,
+            var additional = this.additionalClasses,
                 classes;
 
-            if (_.isString(addtional)) {
-                addtional = this.additionalClasses.split(' ');
+            if (_.isString(additional)) {
+                additional = this.additionalClasses.split(' ');
                 classes = this.additionalClasses = {};
 
-                addtional.forEach(function (name) {
+                additional.forEach(function (name) {
                     classes[name] = true;
                 }, this);
             }