WebGPU: Remove GPUShaderStage hack.

[Mugen87]

Related issue: -

Description

Since there is already a fallback in place for GPUShaderStage in WGSLNodeBuilder, it seems the fallback from WebGPU.js can be removed.

three.js/src/renderers/webgpu/nodes/WGSLNodeBuilder.js

Lines 21 to 34 in d6c03fc

	// GPUShaderStage is not defined in browsers not supporting WebGPU
	const GPUShaderStage = self.GPUShaderStage;
	const wrapNames = {
	[ RepeatWrapping ]: 'repeat',
	[ ClampToEdgeWrapping ]: 'clamp',
	[ MirroredRepeatWrapping ]: 'mirror'
	};
	const gpuShaderStageLib = {
	'vertex': GPUShaderStage ? GPUShaderStage.VERTEX : 1,
	'fragment': GPUShaderStage ? GPUShaderStage.FRAGMENT : 2,
	'compute': GPUShaderStage ? GPUShaderStage.COMPUTE : 4
	};