WebGPURenderer: Fix Shadows PBR

[RenaudRohlinger]

Fixed #30283

This contribution is funded by Utsubo

[github-actions]

📦 Bundle size

Full ESM build, minified and gzipped.

	Before	After	Diff
WebGL	339.52 79.1	339.52 79.1	+0 B +0 B
WebGPU	490.8 136.38	490.81 136.38	+13 B +3 B
WebGPU Nodes	490.26 136.27	490.27 136.28	+13 B +3 B

🌳 Bundle size after tree-shaking

Minimal build including a renderer, camera, empty scene, and dependencies.

	Before	After	Diff
WebGL	465.41 112.15	465.41 112.15	+0 B +0 B
WebGPU	561.37 152.09	561.38 152.09	+13 B +4 B
WebGPU Nodes	516.76 141.66	516.77 141.66	+13 B +3 B