Update AP preference to not be master switch pref

People keep getting confused by the master switch preference for
wireless tethering. The wireless tethering page already has a switch
so this just removes it from the preference and has it take you to
the page when tapped on instead.

Bug: 69423941
Test: robotests
Change-Id: I66d6d3271e83b49ae77f203e7892438d27f96025