gr-change-metadata: Change "Hashtag" label to "Hashtags"

Change-Id: Ie768e70081e33e9435ecb76fd3fb0f891e8e146e
diff --git a/polygerrit-ui/app/elements/change/gr-change-metadata/gr-change-metadata.html b/polygerrit-ui/app/elements/change/gr-change-metadata/gr-change-metadata.html
index 5f88565..5ed7d1d 100644
--- a/polygerrit-ui/app/elements/change/gr-change-metadata/gr-change-metadata.html
+++ b/polygerrit-ui/app/elements/change/gr-change-metadata/gr-change-metadata.html
@@ -239,7 +239,7 @@
       </section>
       <template is="dom-if" if="[[serverConfig.note_db_enabled]]">
         <section class="hashtag">
-          <span class="title">Hashtag</span>
+          <span class="title">Hashtags</span>
           <span class="value">
             <template is="dom-repeat" items="[[change.hashtags]]">
               <gr-linked-chip