FIX: Show replies to the post, not the topic

This makes more sense when reviewing. How many people replied to this
objectionable thing?

app/assets/javascripts/discourse/templates/components/reviewable-item.hbs

@@ -2,8 +2,8 @@
   <div class='reviewable-meta-data'>
     <span class='reviewable-type'>{{reviewable.humanType}}</span>
     <span class='badge-notification new-posts score' title={{i18n "review.scores.score"}}>{{format-score reviewable.score}}</span>
-    {{#if reviewable.topic}}
-    <span class='reply-count'>{{i18n "review.topic_replies" count=reviewable.topic.reply_count}}</span>
+    {{#if reviewable.reply_count}}
+      <span class='reply-count'>{{i18n "review.replies" count=reviewable.reply_count}}</span>
     {{/if}}
     <span class='status'>
       {{#if reviewable.approved}}

app/serializers/reviewable_flagged_post_serializer.rb

@@ -1,3 +1,3 @@
 class ReviewableFlaggedPostSerializer < ReviewableSerializer
-  target_attributes :cooked, :raw
+  target_attributes :cooked, :raw, :reply_count
 end

config/locales/client.en.yml

@@ -408,7 +408,7 @@ en:
         unique_users:
           one: "1 user"
           other: "{{count}} users"
-      topic_replies:
+      replies:
         one: "1 reply"
         other: "{{count}} replies"
       edit: "Edit"