Bump @blockly/dev-tools from 2.3.0 to 2.4.0 (#4936)

Bumps [@blockly/dev-tools](https://github.com/google/blockly-samples/tree/HEAD/plugins/dev-tools) from 2.3.0 to 2.4.0.
- [Release notes](https://github.com/google/blockly-samples/releases)
- [Commits](https://github.com/google/blockly-samples/commits/@blockly/dev-tools@2.4.0/plugins/dev-tools)

---
updated-dependencies:
- dependency-name: "@blockly/dev-tools"
  dependency-type: direct:development
  update-type: version-update:semver-minor
...

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