[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.

CUSTOM_BUNDLE.md とクローズされた #5535 の議論から始めて、現在の scatter トレースのバンドルに関する制約を理解してください。カスタムバンドルで scatter を除外しても、scattergl、scatterternary、またはその他の依存するトレースを壊さずに済むか確認してください。未要求の scatter が安全に除外されるか、scatter を含めたままにする必要がある理由をドキュメントで明確に説明できれば完了です。