fix(docs): remove duplicate https in zh-CN online example links

[coderwei99]

Summary

Fix the online example links in README.zh-CN.md. Four URLs were
incorrectly prefixed with an extra "https://" (e.g.
https://https://plait.pages.dev?init=draw), which made them
unopenable. Removed the duplicate scheme so they match the links in
the English README.md.

This is a documentation-only change; no @plait/* package is affected.

Related Issue

N/A

Validation

• Applicable checks pass: lint, build, and tests
• Relevant documentation and examples were verified or are not applicable

Evidence and compatibility notes:

The corrected URLs now match the English README.md and open correctly:

• https://plait.pages.dev?init=draw
• https://plait.pages.dev?init=mind
• https://plait.pages.dev/graph-viz?init=force-atlas
• https://plait.pages.dev/flow

No public API, behavior, or data compatibility impact.

Changeset

• A changeset was added when required
• No changeset is required

AI Assistance

Did you use AI tools to generate or substantially modify code, tests, or documentation in this pull request?

• No
• Yes

If yes:

• Tool/model:

• AI-assisted work:

• My review and validation:

• I reviewed and understand the AI-assisted changes and can explain and maintain them

Checklist

• The title and description are in English, and the change is focused
• I reviewed and understand every submitted change
• Tests, documentation, and examples were updated when needed
• Public API and data compatibility were considered