Eliminate @response instance variable

app/models/project_services/external_wiki_service.rb

@@ -29,9 +29,10 @@ class ExternalWikiService < Service
   end
 
   def execute(_data)
-    @response = Gitlab::HTTP.get(properties['external_wiki_url'], verify: true) rescue nil
-
-    @response.body if @response.code == 200
+    response = Gitlab::HTTP.get(properties['external_wiki_url'], verify: true)
+    response.body if response.code == 200
+  rescue
+    nil
   end
 
   def self.supported_events