Update systemd dependencies in accordance to moving code to livehandler

[Martchus]

• Make openqa-livehandler.service depend on openqa-websockets.service as it now depends on it for starting/stopping the live view image of running jobs
• Remove dependency on openqa-webui.service as it creates a dependency cycle but the livehandler is not depending on the main web UI directly
  • The dependency was introduced in 8fe15fc7aed but without stating the reasoning.
• See https://progress.opensuse.org/issues/163757