Fix Style/FormatStringToken cop in paperclip color extractor

.rubocop_todo.yml

@@ -83,7 +83,6 @@ Style/FetchEnvVar:
 Style/FormatStringToken:
   Exclude:
     - 'config/initializers/devise.rb'
-    - 'lib/paperclip/color_extractor.rb'
 
 # This cop supports unsafe autocorrection (--autocorrect-all).
 Style/GlobalStdStream:

lib/paperclip/color_extractor.rb

@@ -183,7 +183,7 @@ module Paperclip
     end
 
     def rgb_to_hex(rgb)
-      format('#%02x%02x%02x', rgb.r, rgb.g, rgb.b)
+      format('#%<red>02x%<green>02x%<blue>02x', red: rgb.r, green: rgb.g, blue: rgb.b)
     end
   end
 end