docs(document): fix formatting on getChanges()

Fix #9376

lib/document.js

@@ -3975,32 +3975,41 @@ Document.prototype.$__fullPath = function(path) {
  * Returns the changes that happened to the document
  * in the format that will be sent to MongoDB.
  *
- *  ###Example:
- *   const userSchema = new Schema({
- *     name: String,
- *     age: Number,
- *     country: String
- *   });
- *   const User = mongoose.model('User', userSchema);
- *   const user = await User.create({
- *     name: 'Hafez',
- *     age: 25,
- *     country: 'Egypt'
- *   });
+ * #### Example:
  *
- *   // returns an empty object, no changes happened yet
- *   user.getChanges(); // { }
+ *     const userSchema = new Schema({
+ *       name: String,
+ *       age: Number,
+ *       country: String
+ *     });
+ *     const User = mongoose.model('User', userSchema);
+ *     const user = await User.create({
+ *       name: 'Hafez',
+ *       age: 25,
+ *       country: 'Egypt'
+ *     });
+ *
+ *     // returns an empty object, no changes happened yet
+ *     user.getChanges(); // { }
+ *
+ *     user.country = undefined;
+ *     user.age = 26;
  *
- *   user.country = undefined;
- *   user.age = 26;
+ *     user.getChanges(); // { $set: { age: 26 }, { $unset: { country: 1 } } }
  *
- *   user.getChanges(); // { $set: { age: 26 }, { $unset: { country: 1 } } }
+ *     await user.save();
  *
- *   await user.save();
+ *     user.getChanges(); // { }
  *
- *   user.getChanges(); // { }
+ * Modifying the object that `getChanges()` returns does not affect the document's
+ * change tracking state. Even if you `delete user.getChanges().$set`, Mongoose
+ * will still send a `$set` to the server.
  *
- * @return {Object} changes
+ * @return {Object}
+ * @api public
+ * @method getChanges
+ * @memberOf Document
+ * @instance
  */
 
 Document.prototype.getChanges = function() {