docs: Update pants build command

[HyeockJinKim]

The path required for the LOCKSET setting has changed when using towncrier, reflect this in the documentation.

Checklist: (if applicable)

• Milestone metadata specifying the target backport version
• Mention to the original issue
• Installer updates including:
  • Fixtures for db schema changes
  • New mandatory config options
• Update of end-to-end CLI integration tests in ai.backend.test
• API server-client counterparts (e.g., manager API -> client SDK)
• Test case(s) to:
  • Demonstrate the difference of before/after
  • Demonstrate the flow of abstract/conceptual models with a concrete implementation
• Documentation
  • Contents in the docs directory
  • docstrings in public interfaces and type annotations

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📚 Documentation preview 📚: https://sorna--2945.org.readthedocs.build/en/2945/

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📚 Documentation preview 📚: https://sorna-ko--2945.org.readthedocs.build/ko/2945/

[achimnol]

You may omit the news fragment for this kind of "simple" documentation updates, by applying the skip:changelog label.

[HyeockJinKim]

Oh, I didn't realize that. I'll leave out the segment and add a label.