fix(translations): improve Spanish translations (#12555)

There are still things to improve.

- We're inconsistent with our use of capital letters. There are still
sentences where every word starts with a capital letter, and it looks
ugly (this also happens in English, but to a lesser extent).
- We're inconsistent with the use of punctuation at the end.
- Sentences with variables like {{count}} can result in inconsistencies
if it's 1 and the noun is plural.
- The same thing happens in Spanish, but also with gender. It's
impossible to know without the context in which it's used.

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Co-authored-by: Paul Popus <[email protected]>

Author: GermanJablo