kcms/autostart: enable Accessible properties for actions

Reason for the change

Qt allows setting Accessible properties on actions since version 6.8. We prepared some more descriptive labels for kcm_autostart buttons a year ago, but depended on 6.8 too close to string freeze to enable them for 6.4.

Let's enable them for 6.5 and make using the software with screen readers slightly less confusing. The strings were also slightly tweaked from the existing, commented-out versions to be more compact.

Test plan

Open with orca or accessiblityinspector/accerciser.

Screenshots or screen recordings

N/A

Bugs fixed

N/A