WebGPURenderer: Ignore diagnostic() method in firefox

[sunag]

Related issue: #29258

Not all examples need it, so we can disable it for Firefox for as needed.

[github-actions]

📦 Bundle size

Full ESM build, minified and gzipped.

	Before	After	Diff
WebGL	685.1 kB 169.6 kB	685.1 kB 169.6 kB	+0 B +0 B
WebGPU	822.6 kB 220.8 kB	822.6 kB 220.8 kB	+78 B +28 B
WebGPU Nodes	822.1 kB 220.7 kB	822.2 kB 220.7 kB	+497 B +126 B

🌳 Bundle size after tree-shaking

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

	Before	After	Diff
WebGL	461.9 kB 111.4 kB	461.9 kB 111.4 kB	+0 B +0 B
WebGPU	521.7 kB 140.6 kB	521.7 kB 140.7 kB	+78 B +30 B
WebGPU Nodes	478.3 kB 130.5 kB	478.4 kB 130.5 kB	-43.27 kB +32 B

[ErichDonGubler]

Heads up as a maintainer of Firefox's WGSL shader compiler: Once gfx-rs/wgpu#6148 lands, and it's consumed in Firefox, you should be able to revert this. You can also follow along at bug 1882800.