[SB] Use RootModernization flag helper class in ChipsModernization.

I needed to manually disable RootModernization by changing the flag
helper class, but then realized that didn't disable ChipsModernization
and it caused a crash. This CL isn't strictly necessary at all, it
just helps if we want to disable/enable flags by changing the flag
helper class instead of the flag status.

Bug: N/A
Test: compiles
Flag: com.android.systemui.status_bar_chips_modernization
Change-Id: I7c45cbc02b2a075e977369c2d40a9f3f3aabfa74