feat(MessageEmbed): change toJSON method to return an api-compatible object (#3813)

src/structures/MessageEmbed.js

@@ -317,16 +317,11 @@ class MessageEmbed {
     return this;
   }
 
-  toJSON() {
-    return Util.flatten(this, { hexColor: true });
-  }
-
   /**
-   * Transforms the embed object to be processed.
+   * Transforms the embed to a plain object.
    * @returns {Object} The raw data of this embed
-   * @private
    */
-  _apiTransform() {
+  toJSON() {
     return {
       title: this.title,
       type: 'rich',