Fixing and adding missing pt-br translations

[gtkacz]

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Description

Fixing wrong translations and adding missing ones in PT-BR. Closes #9526.

[lovelydinosaur]

We've generally been managing translations through transifex.
@encode/django-rest-framework should we just deal with them here instead?

[peterthomassen]

I have no experience with Transifex, and thus no preference. What would be the pros and cons?

That said, it may be that this ended up here because the Transifex link in the docs was broken. Here's a fix: #9541

[TGoddessana]

I recently applied to join the team to add a missing translation, but they haven't contacted me. Maybe it would be a good idea to handle the translation here?

[lovelydinosaur]

Cool, yep.

(Also, docs might need editing in this case)