docs: update Rspack tracing file name

[chenjiahan]

Summary

Update Rspack tracing file name. Since Rspack 1.4.0-beta.0, it's rspack.pftrace instead of trace.json.

Related Links

• https://github.com/web-infra-dev/rspack/releases/tag/v1.4.0-beta.0
• feat: support perfetto proto as tracing format rspack#10549

Checklist

• Tests updated (or not required).
• Documentation updated (or not required).

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[Copilot]

Pull Request Overview

This PR updates the documentation to correctly reflect Rspack's new tracing file name, which is rspack.pftrace starting from version 1.4.0-beta.0.

• Changed the file name in the Chinese build-profiling guide from trace.json to rspack.pftrace and noted the change in version history.
• Updated the English build-profiling guide similarly to reference rspack.pftrace with an explanatory note.

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
website/docs/zh/guide/debug/build-profiling.mdx	Updated tracing file reference in the Chinese documentation.
website/docs/en/guide/debug/build-profiling.mdx	Updated tracing file reference in the English documentation.