Remove NsdShim as it is not required

NsdShim is added to make the NsdManagerTest buildable in some old
branch. As a part of migrating to new branch, the nsdShim is not
needed anymore.

Test: atest CtsNetTestCases:android.net.cts.NsdManagerTest
Change-Id: Ia6a9663163a111aa070d88f585ab04918443cb8a