Make footer preferences non-clickable by default

cherry-picked from ag/2301717

Both the footer preference and the TextView they contain
were clickable, which confused some accessibility services.

Bug: 62050563
Test: Verified that switch access no longer offers users
the option of clicking on the footer for accessibility
services and Magnification as well as in the Battery
settings screen.

Change-Id: I5cb13d6268466c690dd38f2b652422d2c3d813b4
Merged-In: I937340fda93f6a8097919e1f86d5d890487370bc