Remove QQS brightness controller

This was not being used and it was leaking ContentObservers

Test: heapdump, switching between splitshade and not splitshade many
times
Test: atest com.android.systemui.qs
Fixes: 218888308

Change-Id: I63501bf573e006f52379192b7b766283fea40dda
Merged-In: I63501bf573e006f52379192b7b766283fea40dda