Fix a11y readout of the day toggles in Time Schedule of Modes

Content description (full day name) replaces TextOn/TextOff (day name initial), and the state description no longer has the day name. As a result:
* the initial readout changes from "Monday, off, M, Switch" to "Off, Monday, Switch"
* when toggling, the name of the day is no longer repeated, and just "On/Off" is announced.

Fixes: 370360007
Test: manual, with Talkback
Flag: android.app.modes_ui
Change-Id: I57bbd7034e1af2836582720a7f4871a79d6644ab