Bump @blockly/dev-tools from 2.1.2 to 2.2.0 (#4756)

Bumps [@blockly/dev-tools](https://github.com/google/blockly-samples/tree/HEAD/plugins/dev-tools) from 2.1.2 to 2.2.0.
- [Release notes](https://github.com/google/blockly-samples/releases)
- [Commits](https://github.com/google/blockly-samples/commits/@blockly/dev-tools@2.2.0/plugins/dev-tools)

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