Fix Catalan locale code in translations filename

[aprat84]

Catalan base language code is ca. The ca_ES code is just a country-specific dialect (Catalan from Spain). Just like en, es and pt are base language codes and en_AU (English from Australia), es_419 (Spanish from LATAM) and pt_BR (Portuguese from Brazil) are dialects.

Catalan in wikipedia
Common IETF primary language subtags

[Nek-]

Hello,

Thank you very much for your contribution! Links to documentation are a real appreciation, you did great.

This is an interesting mistake here. I have no insight about that... It's ok for me to make this change, but if somebody with a little more knowledge about translation may be valid this, that would be great.

[aprat84]

Looking at examples from symfony github or some popular libraries, ca is the way to go:
Symfony Validator
Symfony Security
Carbon
moment.js

I'll put it another way: if I want to use Catalan in symfony, I'll configure it with ca locale. If I do this, symfony translations (validators, security) work well, but this library's don't.

[Nek-]

Thank you very much for your contribution !