Updates to screen security settings UI text per design.

Bug: 5173985

Change-Id: Icdb1873fd9867e3aed7752e90a00c2f725c1fa6a

Edit to lock_after_timeout_summary to rephrase so new option values will
read correctly.

Also, this change includes a fix for embarrassing spelling/grammar mistakes
in Accessibility hint text.
Bug: 5184517