Investigate non-idempotency of the 'make i18n' command

[radinamatic]

Observed behavior

Encountered in #8911 and #8804 (relevant Slack conversation).

Errors and logs

…

Expected behavior

…

User-facing consequences

…

Steps to reproduce

…

Context

…

[radinamatic]

A bit of history 🔍 :

• During the recent string freeze I have run make i18n-download... several times until beginning of November without issues, adding the new locales ha, id and ka, and translations that had been added on Crowdin.
• Problems started when I tried to add the pt-mz locale.
• @indirectlylit took over with some additional changes, merged i18n cleanup #8624 and i18n fixes and updates – includes Mozambican Portuguese #8633, which eventually included the pt-mz locale and translations.
• When I opened Add the final Gujarati and Korean translations #8804, we had the first appearance of pt-mz translations disappearing on my side after running make i18n-download..., while when @indirectlylit run it on his, the translations were included.
• The issue reappeared when I opened Corrected translation in es-es and es-419 #8911, at which point @rtibbles was able to replicate the pt-mz translations disappearing after running make i18n-download... (both of us have the dev environment in Ubuntu, while @indirectlylit works on macOS).
• Finally, I'm again experiencing the same while pulling the recently approved el locale (Greek) from Crowdin: the new locale and translations work perfectly in my dev environment, but pt-mz is missing (again).

For the fast patch @indirectlylit could add the el locale (I opened #8939 pro-forma), which will also add the 2 pending Spanish correct translations, since make i18n-download... works for him and does not delete pt-mz translated strings, and we decided with the implementations team that the Greek translations need to be included in the 0.15, so a partner can do some linguistic QA (therefore I'm changing this issue to P0).

It would be best if we could figure out what the underlying problem is before @indirectlylit wraps up for the holidays (and going forward 🥲).

[indirectlylit]

I'll be taking a look at this in the afternoon