Propose new Code Review -1 text

New Code Review -1 default text has been proposed on a ML thread.
Propose it here so that we can "review" it. If we can agree this should
be updated as in this change a Gerrit admin will have to update
All-Projects directly then this change can be merged.

Fixes-bug: 1258899
Change-Id: I145d393bba6d7ebede7fbcd1f592937a9daadaf9

doc/source/gerrit.rst

@@ -349,7 +349,7 @@ Next, edit `project.config` to look like::
   copyMinScore = true
   function = MaxWithBlock
   value = -2 Do not merge
-  value = -1 I would prefer that you didn't merge this
+  value = -1 This patch needs further work before it can be merged
   value = 0 No score
   value = +1 Looks good to me, but someone else must approve
   value = +2 Looks good to me (core reviewer)