Não registrar mime type de PDF no initializer

[ppires]

Desde 2011 o rails já registra o mime type de PDF automaticamente (nesse commit), e quando o raro crud inicializa novamente aparece um warning na tela:

actionpack-4.2.4/lib/action_dispatch/http/mime_type.rb:163: warning: already initialized constant Mime::PDF
actionpack-4.2.4/lib/action_dispatch/http/mime_type.rb:163: warning: previous definition of PDF was here