Disable the remaining VPN CTS tests on watches.

- Watches don't support VPN apps.
- The HostsideVpnTests CTS tests are already skipped on watches.
- The tests for VpnManager VPNs do run on watches, but there isn't
  actually a way to start a VpnManager VPN on a watch because there is
  no way to display the consent dialog to the user.
- The VpnService CTS tests verify the VpnService API on watches
  bypassing the consent dialogs.
- Because there is no way to start a VPN app on a watch, there's no
  point requiring the VPN CTS tests to pass.

This CL disables the remaining VPN CTS tests on watches. This allows
watches to disable the VPN service, reducing startup time and memory
usage.

Bug: 286240194
Test: atest CtsNetTestCases FrameworksNetTests
Change-Id: Idb7110232ae7e45cafc265cd4f955c2a6b22361c