### Godot version

4.0.2.stable (7a0977c)

### System information

Ubuntu 22.04, x86_64, LLVM

### Issue description

When performing a dedicated server export with:
- a `ShaderMaterial` (a `canvas_item` shader used on a `Panel` in the example below)
- a build with `disable_3d=yes`

the resulting export gives the following error when run:
```
ERROR: Cannot get class 'PlaceholderMaterial'.
   at: instantiate (core/object/class_db.cpp:326)
ERROR: res://main.tscn:Resource of unrecognized type in file: PlaceholderMaterial.
   at: load (core/io/resource_format_binary.cpp:778)
ERROR: Failed loading resource: res://.godot/exported/206107301/export-3070c538c03ee49b7677ff960a3f5195-main.scn. Make sure resources have been imported by opening the project in the editor at least once.
   at: _load (core/io/resource_loader.cpp:223)
ERROR: Failed loading scene: res://main.tscn
   at: start (main/main.cpp:2965)
```

I would expect things to work here without an error - there's no 3D in use here and a normal export with the same build does run as expected.

### Steps to reproduce

1. Build godot with `disable_3d=yes`.
2. Create a new project, and add a `Panel` node.
3. Add a `canvas_item` shader as the material for the `Panel` node.
4. Perform a dedicated server export using the build from step 1.
5. Run the exported binary and observe the error.

### Minimal reproduction project

[DedicatedServer2DTest.zip](https://github.com/godotengine/godot/files/11597444/DedicatedServer2DTest.zip)

ClassDB::add_compatibility_class("RigidBody", "RigidBody3D");
	ClassDB::add_compatibility_class("RigidDynamicBody2D", "RigidBody2D");
	ClassDB::add_compatibility_class("RigidDynamicBody3D", "RigidBody3D");
	ClassDB::add_compatibility_class("Shape", "Shape3D");
	ClassDB::add_compatibility_class("ShortCut", "Shortcut");
	ClassDB::add_compatibility_class("Skeleton", "Skeleton3D");
	ClassDB::add_compatibility_class("SkeletonIK", "SkeletonIK3D");
	ClassDB::add_compatibility_class("SliderJoint", "SliderJoint3D");
	ClassDB::add_compatibility_class("SoftBody", "SoftBody3D");
	ClassDB::add_compatibility_class("SoftDynamicBody3D", "SoftBody3D");
	ClassDB::add_compatibility_class("Spatial", "Node3D");
	ClassDB::add_compatibility_class("SpatialGizmo", "Node3DGizmo");
	ClassDB::add_compatibility_class("SpatialMaterial", "StandardMaterial3D");
	ClassDB::add_compatibility_class("SphereShape", "SphereShape3D");
	ClassDB::add_compatibility_class("SpotLight", "SpotLight3D");
	ClassDB::add_compatibility_class("SpringArm", "SpringArm3D");
	ClassDB::add_compatibility_class("Sprite", "Sprite2D");
	ClassDB::add_compatibility_class("StaticBody", "StaticBody3D");
	ClassDB::add_compatibility_class("StreamTexture", "CompressedTexture2D");
	ClassDB::add_compatibility_class("TextureProgress", "TextureProgressBar");
	ClassDB::add_compatibility_class("VehicleBody", "VehicleBody3D");
	ClassDB::add_compatibility_class("VehicleWheel", "VehicleWheel3D");
	ClassDB::add_compatibility_class("VideoPlayer", "VideoStreamPlayer");
	ClassDB::add_compatibility_class("ViewportContainer", "SubViewportContainer");
	ClassDB::add_compatibility_class("Viewport", "SubViewport");
	ClassDB::add_compatibility_class("VisibilityEnabler", "VisibleOnScreenEnabler3D");
	ClassDB::add_compatibility_class("VisibilityNotifier", "VisibleOnScreenNotifier3D");
	ClassDB::add_compatibility_class("VisibilityNotifier2D", "VisibleOnScreenNotifier2D");
	ClassDB::add_compatibility_class("VisibilityNotifier3D", "VisibleOnScreenNotifier3D");
	ClassDB::add_compatibility_class("VisualServer", "RenderingServer");