nixos/wivrn: remove defaultRuntime (#498724)

      openFirewall = mkEnableOption "the default ports in the firewall for the WiVRn server";

      defaultRuntime = mkEnableOption ''

        WiVRn as the default OpenXR runtime on the system.

        The config can be found at `/etc/xdg/openxr/1/active_runtime.json`.

        Note that applications can bypass this option by setting an active

        runtime in a writable XDG_CONFIG_DIRS location like `~/.config`

      '';

      autoStart = mkEnableOption "starting the service by default";

      highPriority = mkEnableOption "high priority capability for asynchronous reprojection";

        PRESSURE_VESSEL_IMPORT_OPENXR_1_RUNTIMES = "1";

      };

      pathsToLink = [ "/share/openxr" ];

      etc."xdg/openxr/1/active_runtime.json" = mkIf cfg.defaultRuntime {

        source = "${cfg.package}/share/openxr/1/openxr_wivrn.json";

      };

    };

  };

  meta.maintainers = with maintainers; [ passivelemon ];