Do not make pin field highlightable.

When use a physical keyboard or even a a11y service, the textview for
the pin field can be highlighted. Set the property that makes the field
highlightable to false.

Fixes: 309964334
Test: Open pin bouncer with physical keyboard.
Test: Open pin bouncer with talkback.
Test: Open pin bouncer normally.
Flag: NONE

Change-Id: I634b06c0107f914558118de2aedd8baa9bae5637