Bump nanoid and mocha in /bchrpc/regtest (gcash#547)

Removes [nanoid](https://github.com/ai/nanoid). It's no longer used after updating ancestor dependency [mocha](https://github.com/mochajs/mocha). These dependencies need to be updated together.


Removes `nanoid`

Updates `mocha` from 10.1.0 to 10.8.2
- [Release notes](https://github.com/mochajs/mocha/releases)
- [Changelog](https://github.com/mochajs/mocha/blob/main/CHANGELOG.md)
- [Commits](mochajs/mocha@v10.1.0...v10.8.2)

---
updated-dependencies:
- dependency-name: nanoid
  dependency-type: indirect
- dependency-name: mocha
  dependency-type: direct:production
...

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Author: dependabot[bot]