Revert "Add an API to listen for changes in network blocked status of an uid."

This reverts commit 7dc302d6.

Reason for revert: Breaking build - b/183106805
Bug: 183106805
Merged-In: Ib9949b8619c6b148f73630b314c4113d76c31ec1
Change-Id: I9789ed81e630f49c71034b6917188983bd11d774