removing bracket typo from rest_api docs (#566)

removing extra bracket from `rest_api` docs

sources/rest_api/README.md

@@ -137,7 +137,7 @@ Possible paginators are:
 Usage example of the `JSONLinkPaginator`, for a response with the URL of the next page located at `paging.next`:
 ```python
 "paginator": JSONLinkPaginator(
-    next_url_path="paging.next"]
+    next_url_path="paging.next"
 )
 ```