[l10n] Improve Finnish (fi-FI) locale

[sambbaahh]

• [x] I have followed (at least) the PR section of the contributing guide.

• #3211

[mui-bot]

Localization writing tips :writing_hand:

Seems you are updating localization :earth_africa: files.

Thank you for contributing to the localization! :tada: To make your PR perfect, here is a list of elements to check: :heavy_check_mark:

• [ ] Verify if the PR title respects the release format. Here are two examples (depending if you update or add a locale file)

  [l10n] Improve Swedish (sv-SE) locale [l10n] Add Danish (da-DK) locale

• [ ] Update the documentation of supported locales by running pnpm l10n
• [ ] Clean files with pnpm prettier.

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[oliviertassinari]

@sambbaahh Thanks