WebGPURenderer: Clean up.

examples/jsm/renderers/webgpu/nodes/ShaderLib.js

@@ -8,7 +8,7 @@ NODE_HEADER_VARYS
 
 void main(){
 	NODE_BODY_VARYS
-	gl_Position = NODE_GL_POSITION;
+	gl_Position = NODE_MVP;
 }`,
 		fragmentShader: `#version 450
 

examples/jsm/renderers/webgpu/nodes/WebGPUNodeBuilder.js

@@ -49,7 +49,7 @@ class WebGPUNodeBuilder extends NodeBuilder {
 
 			}
 
-			this.addSlot( 'vertex', new NodeSlot( mvpNode, 'GL_POSITION', 'vec4' ) );
+			this.addSlot( 'vertex', new NodeSlot( mvpNode, 'MVP', 'vec4' ) );
 
 			if ( material.colorNode !== undefined ) {