docs: quote pip extras install examples

[nyxst4ck]

Summary

• Quote pip install examples that include extras.

Why

• Shells such as zsh can expand unquoted bracket expressions before pip receives them.

Scope

• Files changed:
• docs/dependency-locking.md
• This does not change dependencies or runtime behavior.

Testing

• git diff --check

Maintainer Fit

• Small install-command correctness fix.
• Duplicate PR search terms checked: quote pip extras, quote optional dependency, zsh pip install extras, pip extras install examples

[Panniantong]

感谢贡献。该文档修复已在 #578 以保留你作者身份的提交 6e92782 合并到 main，并通过 zsh 参数解析测试与完整 CI。关闭此已被替代的旧 PR。