[CHORE]: remove `scatter` trace from custom bundle

Quoted from https://github.com/plotly/plotly.js/blob/main/CUSTOM_BUNDLE.md:

Please note that the scatter trace is currently included in all bundles and cannot be removed. This behaviour may change in the future, so we recommend that you explicitly include scatter anyway if you need it in your bundle.

There was previously an attempt to make scatter optional in #5535, but that PR was closed without being merged.

Since plotly.js is relatively large even when using a custom bundle, being able to exclude unused traces such as scatter would help further reduce the bundle size.

I'm not sure how much bundle size reduction this would result in, since scattergl, scatterternary and some other traces reuse parts of the scatter implementation. Still, it seems useful for custom bundles to avoid including trace modules that are not explicitly requested where possible.

Would it be worth to re-consider this optimization?

If scatter still needs to be included for architectural reasons, it may be worth updating the documentation? Since the PR is closed.

从 CUSTOM_BUNDLE.md 和已关闭的 #5535 讨论开始，以了解当前 scatter trace 打包的限制。检查自定义 bundle 是否可以排除 scatter，同时不破坏 scattergl、scatterternary 或其他依赖的 trace。完成的标准是：未请求的 scatter 被安全排除，或者文档清楚地解释为什么必须继续包含它。