Remove deprecated Import model (#34371)

config/initializers/paperclip.rb

@@ -169,7 +169,7 @@ else
 end
 
 Rails.application.reloader.to_prepare do
-  Paperclip.options[:content_type_mappings] = { csv: Import::FILE_TYPES }
+  Paperclip.options[:content_type_mappings] = { csv: %w(text/plain text/csv application/csv) }
 end
 
 # In some places in the code, we rescue this exception, but we don't always