VideoTexture: Cancel rVFC on Dispose

[ycw]

Description

This PR ensures that onUpdate wouldn't be called after dispose().

[github-actions]

📦 Bundle size

Full ESM build, minified and gzipped.

	Before	After	Diff
WebGL	337.69 78.76	337.69 78.76	+0 B +0 B
WebGPU	557.69 154.41	557.69 154.41	+0 B +0 B
WebGPU Nodes	556.61 154.19	556.61 154.19	+0 B +0 B

🌳 Bundle size after tree-shaking

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

	Before	After	Diff
WebGL	468.91 113.45	468.91 113.45	+0 B +0 B
WebGPU	633.32 171.43	633.32 171.43	+0 B +0 B
WebGPU Nodes	588.45 160.78	588.45 160.78	+0 B +0 B

[mrdoob]

Initially zero or -1?