[Settings][Test] Fix Junit test failure - MobileNetworkSwitchControllerTest

android.test.UiThreadTest has been deprecated.

This is a change migrate it into androidx.test.annotation.UiThreadTest

Bug: 174832214
Change-Id: I38f35e7602a269a018510723c199a7259d704b4e
Test: atest -c MobileNetworkSwitchControllerTest