Fix typos in spanish translations

[gusdleon]

A translation was wrong in all spanish variants

[mgallien]

@gusdleon thanks for the contribution
unfortunately a PR is not going to work to fix translations as we synchronize them from transifex (see https://nextcloud.com/translation/)
We once a day update the translations from transifex and that would override the changes from your PR
I will close the PR and I really hope you will do the same via transifex
please let me know

[gusdleon]

Hey!
Thanks for the heads up, I have already requested access to the project on Transifex, waiting for approval.