docs: Fix typo Argila -> Argilla

[louisguitton]

Description

I've noticed an env variable in the docs with the following typo: ARGILA instead of ARGILLA, so I fix it.

Type of change

(Remember to title the PR according to the type of change)

• Documentation update

How Has This Been Tested

(Please describe the tests that you ran to verify your changes.)

• sphinx-autobuild (read Developer Documentation for more details)

Checklist

• I added relevant documentation
• I followed the style guidelines of this project
• I did a self-review of my code
• I made corresponding changes to the documentation
• My changes generate no new warnings
• I filled out the contributor form (see text above)
• I have added relevant notes to the CHANGELOG.md file (See https://keepachangelog.com/)

[jfcalvo]

@louisguitton thank you very much for the fix!