Accessibility changes for radio button on clocks

This CL sets the important for a11y attribute on radio buttons to be
false which makes sure that they aren't individually selectable when
user has enabled talkback.

Bug: b/280937148
Test: Tested by building and installing picker, and enabling talkback
service.

Change-Id: I97008dd9573b279568bcec50ccc2f5b3f3705668