Changed talkback string for import cancel button

Changed the content description for cancel import button.
Infeasable to remove 'button' from talkback message because
talkback inserts this into the string itself. So message has been
changed from 'Cancel import Button' to 'Cancel Button'

Test: Verified message is being read out as intended.

Bug: 32975964
Change-Id: I7027a82384e1b30e284606f3fd87d5675e8509bc