Bump asttokens from 2.2.1 to 2.4.0

Bumps [asttokens](https://github.com/gristlabs/asttokens) from 2.2.1 to 2.4.0.
- [Commits](gristlabs/asttokens@2.2.1...v2.4.0)

---
updated-dependencies:
- dependency-name: asttokens
  dependency-type: indirect
  update-type: version-update:semver-minor
...

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