Fix docs to say labels are laid out alphabetically

The labels have been always laid out alphabetically due to the fact that
they're passed as a dict, which does not guarantee order across
different labels. For more details, please see the code change[1].

[1]: https://gerrit-review.googlesource.com/#/c/gerrit/+/60246/

Change-Id: I6726ff28dd8830499747296c112048b4892dca3e
diff --git a/Documentation/config-labels.txt b/Documentation/config-labels.txt
index 532b8c42..c53d1fd 100644
--- a/Documentation/config-labels.txt
+++ b/Documentation/config-labels.txt
@@ -166,9 +166,7 @@
 [[label_layout]]
 === Layout
 
-Labels are laid out in the order they are specified in project.config,
-with inherited labels appearing first, providing some layout control to
-the administrator.
+Labels are laid out in alphabetical order.
 
 [[label_name]]
 === `label.Label-Name`