XRManager: silence opaque framebuffer warning

[cabanier]

Addresses #31193

[github-actions]

📦 Bundle size

Full ESM build, minified and gzipped.

	Before	After	Diff
WebGL	337.4 78.67	337.4 78.67	+0 B +0 B
WebGPU	553.64 153.44	553.76 153.47	+123 B +30 B
WebGPU Nodes	552.99 153.28	553.11 153.31	+123 B +31 B

🌳 Bundle size after tree-shaking

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

	Before	After	Diff
WebGL	468.59 113.32	468.59 113.32	+0 B +0 B
WebGPU	628.59 170.16	628.72 170.19	+123 B +36 B
WebGPU Nodes	583.45 159.5	583.57 159.53	+123 B +32 B

[cabanier]

@Mugen87 I addressed your comments and also marked the others parameters with an _