Remove the feature flag and dead code for the old time zone picker

This commit backports commit 6be6c5820639c1f7ed60dd2a03dab80cbb1b5afb
to aosp/master.

Bug: 72376227
Test: build only
Merged-In: I332077a67cc9f9c83b298e25feea71463e1ee98b
Change-Id: I332077a67cc9f9c83b298e25feea71463e1ee98b
(cherry picked from commit 6be6c5820639c1f7ed60dd2a03dab80cbb1b5afb)
10 files changed