Improve warning when XR shaders are not enabled

(cherry picked from commit d8f2768b90b7b11340cb297dfaaea51f7e75f95f)

scene/3d/xr_nodes.cpp

@@ -623,7 +623,7 @@ PackedStringArray XROrigin3D::get_configuration_warnings() const {
 
 	bool xr_enabled = GLOBAL_GET("xr/shaders/enabled");
 	if (!xr_enabled) {
-		warnings.push_back(RTR("XR is not enabled in rendering project settings. Stereoscopic output is not supported unless this is enabled."));
+		warnings.push_back(RTR("XR shaders are not enabled in project settings. Stereoscopic output is not supported unless they are enabled. Please enable `xr/shaders/enabled` to use stereoscopic output."));
 	}
 
 	return warnings;