Update the usage of UserHandle.getUid

UserHandle.getUid() from a UserHandle is updated to a method on
UserHandle itself based on API review feedback. Thus, update
the usage in the test.

Bug: 184735865
Test: Test: atest android.app.cts.UserHandleTest
Change-Id: I3fae62c1ee29c308cdfde705d775fb029c1c913f
1 file changed