Add missing delimiter in rest-api-changes.txt

This apparently slipped past Asciidoctor's parser but Asciidoc rejects
it.

Change-Id: I60cee2e761390add6c3450f714eb32c3aa93f4db
diff --git a/Documentation/rest-api-changes.txt b/Documentation/rest-api-changes.txt
index 0ec5cd8..08411f5 100644
--- a/Documentation/rest-api-changes.txt
+++ b/Documentation/rest-api-changes.txt
@@ -176,6 +176,7 @@
 * `DRAFT_COMMENTS`: include the `has_draft_comments` field for
   revisions. Only valid when the `CURRENT_REVISION` or `ALL_REVISIONS`
   option is selected.
+--
 
 [[current-commit]]
 --