Update viewComposers.php

### Error

The request "http://localhost/packages/frozennode/administrator/js/plupload/js/i18n/pt-BR.js"  results in 404 error.

### Proposal

All "i18n files" from pupload own name in lower case, and in the case of languages ​​like "pt-BR" or "fr-CA", the ".js" file requested results in 404 error.

This correction set the language to lower case only to pupload.