nixos/wivrn: remove defaultRuntime (#498724)

nixos/modules/services/video/wivrn.nix

@@ -80,14 +80,6 @@ in
 
       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";
@@ -247,9 +239,6 @@ in
         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 ];