Add @TestApi to Context.updateDeviceId

CTS tests have already been added in DeviceAssociationTest, but
that CL missed adding the annotation in the method.

This method, even if @hide, is necessary for key framework
behaviors to allow for implicit device associations to work well.

Bug: 266091657
Test: atest DeviceAssociationTest
Change-Id: I171b14379a21f88f3111206e665c8af41a6957e0