Update highlight.js to version 9.4.0 🚀

[greenkeeperio-bot]

Hello :wave:

:rocket::rocket::rocket:

highlight.js just published its new version 9.4.0, which is not covered by your current version range.

If this pull request passes your tests you can publish your software with the latest version of highlight.js – otherwise use this branch to work on adaptions and fixes.

Happy fixing and merging :palm_tree:

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[nebrius]

Disabled greenkeeper for now so closing