factory-reset(-app): remove --experimental flag

[sosthene-nitrokey]

I added the same warning as in update, but it appears it is just a string without any User-visible behaviour. Should this be changed to local_print?

Changes

• Remove the required --experimental flag for the factory-reset commands

Checklist

Make sure to run make check and make fix before creating a PR, otherwise the CI will fail.

• [ ] tested with Python3.9
• [x] signed commits
• [x] updated documentation (e.g. parameter description, inline doc, docs.nitrokey)
• [ ] added labels

[daringer]

yup, please use local_print otherwise it won't be shown