fix(deps): update lumino packages

[renovate[bot]]

This PR contains the following updates:

Package	Change	Age	Adoption	Passing	Confidence
@lumino/default-theme	2.1.5 -> 2.1.6
@lumino/widgets	2.3.2 -> 2.4.0

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Release Notes

jupyterlab/lumino (@​lumino/default-theme)

### [`v2.1.6`](https://togithub.com/jupyterlab/lumino/compare/@lumino/default-theme@2.1.5...@lumino/default-theme@2.1.6) [Compare Source](https://togithub.com/jupyterlab/lumino/compare/@lumino/default-theme@2.1.5...@lumino/default-theme@2.1.6)

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