Skip starting VpnManagerService for Wear devices

VPN management is not currently working/supported on Wear, so we do not
need start to SystemService. The SystemService was also not started in
the previous Wear OS version.

Bug: 340928692
Test: manual
Flag: android.server.allow_removing_vpn_service
Change-Id: I3e0ef16287658e4f36b142d7c7738bf200f695a1