Update project highlight.js to 8.4

libgrabber updated project highlight.js to 8.4.

@highlightjs

### Metadata information

```json
{
  "metadata": {
    "packageManager": "github",
    "name": "highlight.js",
    "repo": "highlightjs/cdn-release",
    "files": {
      "basePath": "build/",
      "include": ["highlight.min.js", "./languages/*.min.js", "./styles/*.min.css"],
      "exclude": []
    },
    "path": "/home/jsdelivr/files/highlight.js",
    "localVersions": ["7.3.0-b", "7.3.0", "7.5.0", "8.0.0", "8.2.0", "8.3.0"],
    "remoteVersions": ["8.2", "8.3", "8.4"],
    "branchVersions": []
  },
  "version": "8.4",
  "updated": true,
  "updatePath": "/home/jsdelivr/files/highlight.js/8.4.0",
  "branch": "highlight.js/8.4"
}
```