My jetpack: Hide backup failure notice when backups are deactivated (#43568)

* Fix typo in backup status

* Fix the grammar and language for the error message

Error messages should not be too technical for the users as they might not know what a "site attribute" is or what the heck a "general kill switch" is.

* Hide the notice when backups are deactivated

* Add changelog

Committed via a GitHub action: https://github.com/Automattic/jetpack/actions/runs/15249443008

Upstream-Ref: Automattic/jetpack@f905f11

Author: manzoorwanijk