[Tails-l10n] [fr](review) news/social_contract

Hello, I translate the social contract. It was more difficult than
usually because it's more politics than technical.
Please review.

Repo: https://git-tails.immerda.ch/xin/tails/
Branch: translate/socialcontract
Last Commit: df3ab5e67f04c5afc9baa14e0af5d8bc44ffb98f

Cheers.
xin