Migrate to best practise to read network state

`getNetworkInfo()` has been deprecated, while the new method can
 guarantee the device has an actual network connection.

Bug: b/358407371
Test: atest core/tests/coretests/src/android/util/NtpTrustedTimeTest
Test: Treehugger
Change-Id: I8c188859385c2b499280af5c4f27623c8e7dc29d