Use java.util.Objects

This is a follow up CL for I451544fba746a76618.

This CL replaces libcore.util.Objects with java.util.Objects as
java.util.Objects is getting more and more widely used in
Android. There should be no behavioural change anyway.

Change-Id: Id9568ee98aa3845588017c3711e7d03a3481beea
1 file changed