Fix incorrect formatting in json documentation

Change-Id: Idaf47978ddd09c9f7a5708efb7d70afcfb8899f8
diff --git a/Documentation/json.txt b/Documentation/json.txt
index 680705c6..4034050 100644
--- a/Documentation/json.txt
+++ b/Documentation/json.txt
@@ -141,8 +141,7 @@
 by:: Reviewer of the patch set in <<account,account attribute>>.
 
 [[refUpdate]]
-refUpdate
---------
+== refUpdate
 Information about a ref that was updated.
 
 oldRev:: The old value of the ref, prior to the update.