rubocop: fix various style issues.

app/models/artist_url.rb

@@ -29,17 +29,17 @@ class ArtistUrl < ApplicationRecord
 
       # the strategy won't always work for twitter because it looks for a status
       url = url.downcase if url =~ %r!^https?://(?:mobile\.)?twitter\.com!
-        
+
       begin
         source = Sources::Strategies.find(url)
-  
+
         if !source.normalized_for_artist_finder? && source.normalizable_for_artist_finder?
           url = source.normalize_for_artist_finder
         end
       rescue Net::OpenTimeout, PixivApiClient::Error
         raise if Rails.env.test?
       end
-      
+
       url = url.gsub(/\/+\Z/, "")
       url = url.gsub(%r!^https://!, "http://")
       url + "/"