update annotations

app/models/stylesheet_cache.rb

@@ -43,11 +43,11 @@ end
 # Table name: stylesheet_cache
 #
 #  id         :integer          not null, primary key
-#  target     :string           not null
-#  digest     :string           not null
+#  target     :string(255)      not null
+#  digest     :string(255)      not null
 #  content    :text             not null
-#  created_at :datetime         not null
-#  updated_at :datetime         not null
+#  created_at :datetime
+#  updated_at :datetime
 #  theme_id   :integer          default(-1), not null
 #  source_map :text
 #