Use raw string when setting wifi preference title.

This is necessary for talkback to correctly recognize content
description on the whole viewgroup.

Merged-In: Ic792102b269b9a8db09c632f7e70d8773048c840
Change-Id: I555f94afcd6f4c681bb16dd23d94b2ae0fd4c116
Fixes: 65202862
Test: robotests