Remove unused state fields

assets/js/src/newsletters/breadcrumb.jsx

@@ -26,7 +26,6 @@ class Breadcrumb extends React.Component {
     ];
 
     this.state = {
-      step: null,
       steps,
     };
   }

assets/js/src/newsletters/listings/tabs.jsx

@@ -7,7 +7,6 @@ import PropTypes from 'prop-types';
 
 class ListingTabs extends React.Component {
   state = {
-    tab: null,
     tabs: Hooks.applyFilters('mailpoet_newsletters_listings_tabs', [
       {
         name: 'standard',

assets/js/src/newsletters/send/congratulate/congratulate.jsx

@@ -64,7 +64,6 @@ class Congratulate extends React.Component {
     super(props);
     this.state = {
       loading: true,
-      fail: false,
       newsletter: null,
       testingPassed: false,
       timeStart: moment(),