Fix eslint rules

[MAILPOET-1348]

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

@@ -1,14 +1,7 @@
-define(
-  [
-    'mailpoet',
-    'wp-js-hooks',
-    'newsletters/types/welcome/scheduling.jsx',
-  ],
-  (
-    MailPoet,
-    Hooks,
-    Scheduling
-  ) => {
+import MailPoet from 'mailpoet';
+import Hooks from 'wp-js-hooks';
+import Scheduling from 'newsletters/types/welcome/scheduling.jsx';
+
 let fields = [
   {
     name: 'subject',
@@ -75,7 +68,7 @@ define(
 
 fields = Hooks.applyFilters('mailpoet_newsletters_3rd_step_fields', fields);
 
-    return {
+module.export = {
   getFields: function getFields() {
     return fields;
   },
@@ -85,5 +78,3 @@ define(
     };
   },
 };
-  }
-);