Using comments inside of a `json` codeblock creates hard to read text

[mainrs]

https://github.com/dhall-lang/dhall-haskell/issues/2374#issue-1119871430

The code block looks like this:

```json
// .vscode/settings.json
{
    "vscode-dhall-lsp-server.server.contextFile": "${workspaceRoot}/ApiContext.dhall"
}
```

[unseen-ninja]

Fixed. This should also fix some of the other issues the prettylights highlighting still had. c: