docs: improve README examples of lib/node_modules/@stdlib/constants/u…

[BeastMasterGrinder]

Resolves #1566 .

Description

improve README examples of constants/unicode namespace

Related Issues

No

This pull request:

• resolves #1566
• fixes #1566

Questions

Any questions for reviewers of this pull request?

No.

Other

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No.

Checklist

Please ensure the following tasks are completed before submitting this pull request.

• [ ] Read, understood, and followed the contributing guidelines.
• [ ] Searched for existing issues and pull requests.
• [ ] The issue name begins with RFC:

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