WebGLRenderer: Fix shadow bias with reversed depth buffer.

[Mugen87]

Related issue: #31998

Description

After testing all combinations of lights and shadow map types, only point light PCF shadows with reversed depth buffer require an different shadow bias handling. For all other permutations, #32751 already ensured a consistent handling.

[github-actions]

📦 Bundle size

Full ESM build, minified and gzipped.

	Before	After	Diff
WebGL	355.34 84.48	355.36 84.48	+21 B +3 B
WebGPU	621.04 172.46	621.04 172.46	+0 B +0 B
WebGPU Nodes	619.64 172.22	619.64 172.22	+0 B +0 B

🌳 Bundle size after tree-shaking

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

	Before	After	Diff
WebGL	487.57 119.37	487.59 119.38	+21 B +4 B
WebGPU	691.97 187.85	691.97 187.85	+0 B +0 B
WebGPU Nodes	641.77 175.01	641.77 175.01	+0 B +0 B