Show edit icon for topic only if it is not readonly

Release-Notes: skip
Change-Id: I1859785435014765deb4dc23240ffcfd3d6a67b2

polygerrit-ui/app/elements/change/gr-change-metadata/gr-change-metadata_html.ts

diff --git a/polygerrit-ui/app/elements/change/gr-change-metadata/gr-change-metadata_html.ts b/polygerrit-ui/app/elements/change/gr-change-metadata/gr-change-metadata_html.ts
index 25dab25..c81c094 100644
--- a/polygerrit-ui/app/elements/change/gr-change-metadata/gr-change-metadata_html.ts
+++ b/polygerrit-ui/app/elements/change/gr-change-metadata/gr-change-metadata_html.ts
@@ -421,7 +421,7 @@
             placeholder="[[_computeTopicPlaceholder(_topicReadOnly)]]"
             read-only="[[_topicReadOnly]]"
             on-changed="_handleTopicChanged"
-            show-as-edit-pencil="true"
+            show-as-edit-pencil="[[!_topicReadOnly]]"
             autocomplete="true"
             query="[[queryTopic]]"
           ></gr-editable-label>