Change android.permission.RESTRICTED_VR_ACCESS to SystemAPI

android.permission.RESTRICTED_VR_ACCESS is currently an open API. But
since it can only be used by System Apps because of it's protection
level which is "signature|preinstalled". Change this to a @SystemApi.

Bug: 37724255
Test: run gts --module GtsPermissionTestCases
1. Run with two apps having android.permission.RESTRICTED_VR_ACCESS
   before change -- fails.
2. Run with two appshaving android.permission.RESTRICTED_VR_ACCESS
   after this change -- passes.

Change-Id: I9e640b0794fa16d03ba22e8aa75175e7e08dd88b
Signed-off-by: Karthik Ravi Shankar <karthikrs@google.com>