Fix display of related changes

The fix for displaying submitted together changes didn't update the
observer for related changes, so fixing one thing broke the other. This
change corrects that, and observes related changes in the same manner as
submitted together changes.

Bug: Issue 10003
Change-Id: I4b8e3b229c14cda8a5e28a376e58e976d8a3349d
(cherry picked from commit 364757cce23192a9d6da32535658b77af5f9227c)
diff --git a/polygerrit-ui/app/elements/change/gr-related-changes-list/gr-related-changes-list.js b/polygerrit-ui/app/elements/change/gr-related-changes-list/gr-related-changes-list.js
index f2cfe87..39f4d8d 100644
--- a/polygerrit-ui/app/elements/change/gr-related-changes-list/gr-related-changes-list.js
+++ b/polygerrit-ui/app/elements/change/gr-related-changes-list/gr-related-changes-list.js
@@ -82,7 +82,7 @@
     ],
 
     observers: [
-      '_resultsChanged(_relatedResponse.changes, _submittedTogether, ' +
+      '_resultsChanged(_relatedResponse, _submittedTogether, ' +
           '_conflicts, _cherryPicks, _sameTopic)',
     ],