fixing "already initialized constant PDF" warning
fixing "already initialized constant PDF" warning

after this commit https://github.com/rails/rails/commit/d73269ba53992d8a01e5721aad3d23bc2b11dc4f rails already initialized pdf mime type, so we don't need to do it always.
fortesinformatica/jasper-rails,miltecnologia/jasper-rails,aquinofb/jasper-rails