[Testing] Use AndroidJUnit4 instead in MobileNetworkUtilsTest am: 2e763e52cf

Original change: https://android-review.googlesource.com/c/platform/packages/apps/Settings/+/1614986

MUST ONLY BE SUBMITTED BY AUTOMERGER

Change-Id: I4d5ff0ee3f8af2de5387d61094be0d9f3c35ce6b