Update apiary.apib

Co-authored-by: mrnyax <nyakoria@gmail.com>

apiary.apib

@@ -1422,7 +1422,7 @@ The example response includes the pagination URLs and query parameters in the `l
 
 If you're managing a large number of users, you can benefit from the query params `includeCustomField` and `excludeProperties`.
 
-By default all custom field is returned nested in the user model. 
+By default all custom fields are returned nested in the user model.
 Using the `includeCustomField` can help reduce the data transferred and fetch the only custom fields that are needed. 
 When specified, only the few custom fields are returned, that are found with the given key passed in the param value. 
 To include more than one simply append N times the `&includeCustomField={Key}` to the request.