Remove throttling difference for GSM

Removing a difference between GSM and other
devices.

Throttling was added to CDMA in commit:
https://android.googlesource.com/platform/frameworks/base/+/aeff5fd8eb17bc0f611918d6482139c1921e7b60
(bug 2251845).

The bug justification was that CDMA was receiving NITZ
updates too regularly, which was impacting device
performance.

If GSM receives updates at a slower rate the throttling
should be a no-op so there’s no reason to have separate paths.

atest FrameworksTelephonyTests:NitzStateMachineTest \
FrameworksTelephonyTests:ServiceStateTrackerTest

Bug: 63743683
Test: build / test / see above
Change-Id: I36d580436e3bbb8c47d453a80eb81686c57809b3