Disable is:mergeable by default

Bug: Issue 14528
Change-Id: I0da471a74c5edaab329f7f20fa992b279efefcfa
diff --git a/Documentation/config-gerrit.txt b/Documentation/config-gerrit.txt
index 5f2ea09..1c98b9af 100644
--- a/Documentation/config-gerrit.txt
+++ b/Documentation/config-gerrit.txt
@@ -1407,7 +1407,7 @@
   query operator. Gerrit does not serve `mergeable` in
   link:rest-api-changes.html#change-info[ChangeInfo].
 
-Default is `REF_UPDATED_AND_CHANGE_REINDEX`.
+Default is `NEVER`.
 
 [[change.move]]change.move::
 +