Update fr_FR app translation for 3.9.1

[pljones]

Hi @jujudusud, We are getting ready for the 3.9.1 release. No further changes to translatable strings are currently planned for this release.

We would be happy if you updated the Jamulus software translations for fr_FR by 2022-10-08.

Please

• Update your fork from jamulussoftware/jamulus master and create a working branch
• Update translations using Qt Linguist in your fork,
• Commit and push your changes and reference this Issue,
• Open a Pull Request before 2022-10-08

Suggested commit and PR message:

Update fr_FR app translation for 3.9.1

Fixes #2867

Further documentation can be found in TRANSLATING.md.

Thanks for contributing to Jamulus!