[Tails-l10n] [fr](review) french updates

Hello:

I have made a branch with changes from weblate to French files.

Changes are mainly header, links, strings already translated on other files, fuzzy strings. Little corrections.

I have edited them, they are not only the product of an automated script! :D

I did `git add -p` on everything, but sometimes some headers slipped because it was hard to split the hunks...

Please review

Repo: git.tails.boum.org:emmapeel/tails
 * [branch]          fr_updates
Last commit:     6c6acd397858a73283b86f0a4f8e3aa117a7054d