bulk delete API method requires empty parameters

Requiring no parameters for the bulk delete operation actually means you need to supply an empty JSON object for the parameters or the API rejects the request.

docs/api.md

@@ -366,7 +366,7 @@ The following methods are supported:
 - `modify_tags`
   - Requires `parameters`: `{ "add_tags": [LIST_OF_TAG_IDS] }` and / or `{ "remove_tags": [LIST_OF_TAG_IDS] }`
 - `delete`
-  - No `parameters` required
+  - Empty `parameters` required: `{ }`
 - `redo_ocr`
   - No `parameters` required
 - `set_permissions`