Fix incorrect Portuguese translation

The Portuguese translation file contains an error: the translation for "Extension" is "Extensão", not "Ramal".

"Ramal" is used exclusively for phone extensions (the kind you have to dial extra digits to get to the right device). This is extremely confusing because the certificate details may contain information related to phone numbers, but this is not one of them.

I'm not sure this is the right channel to propose a change, so any help on this direction will be appreciated.