Ensure that we use vote$ to set vote-attribute

Without this it won't actually add the attribute

Change-Id: I1c06104a4ed54b397373f76defa88464f02a3336
diff --git a/polygerrit-ui/app/elements/change/gr-label-score-row/gr-label-score-row_html.ts b/polygerrit-ui/app/elements/change/gr-label-score-row/gr-label-score-row_html.ts
index 618403c..9ac6d05 100644
--- a/polygerrit-ui/app/elements/change/gr-label-score-row/gr-label-score-row_html.ts
+++ b/polygerrit-ui/app/elements/change/gr-label-score-row/gr-label-score-row_html.ts
@@ -126,7 +126,7 @@
         >
           <gr-button
             role="radio"
-            vote="[[_computeVoteAttribute(value, index, _items.length)]]"
+            vote$="[[_computeVoteAttribute(value, index, _items.length)]]"
             voteChip
           >
             [[value]]