DEV: Clean up thumbnail tests correctly

spec/integration/topic_thumbnail_spec.rb

@@ -10,7 +10,7 @@ describe "Topic Thumbnails" do
 
   context 'latest' do
     def get_topic
-      Discourse.redis.del(topic.thumbnail_job_redis_key([]))
+      Discourse.redis.del(topic.thumbnail_job_redis_key(Topic.thumbnail_sizes))
       get '/latest.json'
       response.parsed_body["topic_list"]["topics"][0]
     end

spec/serializers/topic_view_serializer_spec.rb

@@ -60,7 +60,7 @@ describe TopicViewSerializer do
       it 'should have thumbnails' do
         SiteSetting.create_thumbnails = true
 
-        Discourse.redis.del(topic.thumbnail_job_redis_key([]))
+        Discourse.redis.del(topic.thumbnail_job_redis_key(Topic.thumbnail_sizes))
         json = nil
 
         expect do