Fix faulty regex for syntax highlighter · source-academy/js-slang@2464961

The following actions use a deprecated Node.js version and will be forced to run on node20: coverallsapp/github-action@master. For more info: https://github.blog/changelog/2024-03-07-github-actions-all-actions-will-run-on-node20-instead-of-node16-by-default/

'f' is defined but never used. Allowed unused args must match /^_/u

'_' is assigned a value but never used

'reject' is defined but never used. Allowed unused args must match /^_/u

'stash' is defined but never used. Allowed unused args must match /^_/u

'stash' is defined but never used. Allowed unused args must match /^_/u

'stash' is defined but never used. Allowed unused args must match /^_/u

'stash' is defined but never used. Allowed unused args must match /^_/u

'stash' is defined but never used. Allowed unused args must match /^_/u

'stash' is defined but never used. Allowed unused args must match /^_/u

'stash' is defined but never used. Allowed unused args must match /^_/u

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