WebGPURenderer: Fix output depth struct

[sunag]

Fixes #30476

Description

Fix output depth when used outputStruct().

[github-actions]

📦 Bundle size

Full ESM build, minified and gzipped.

	Before	After	Diff
WebGL	336.42 78.33	336.42 78.33	+0 B +0 B
WebGPU	518.01 143.92	518 143.91	-17 B -11 B
WebGPU Nodes	517.48 143.81	517.46 143.8	-17 B -11 B

🌳 Bundle size after tree-shaking

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

	Before	After	Diff
WebGL	465.41 112.17	465.41 112.17	+0 B +0 B
WebGPU	589.89 160.02	589.87 160	-17 B -14 B
WebGPU Nodes	545.26 149.56	545.24 149.54	-17 B -15 B