Code removes newline at the end of .json files

[moi90]

• VSCode Version: 1.50.1
• OS Version: Ubuntu 18.04.5 LTS

Steps to Reproduce:

1. Start without extensions: code --disable-extensions
2. Open JSON file. Add newlines at the end of the file.
3. "Format Document".

The newlines are gone.

Does this issue occur when all extensions are disabled?: Yes.

Settings:

{
"files.trimFinalNewlines": false,
}

[aeschli]

The JSON formatter removes all 'unnecessary' new lines.

The request to preserve new lines is #23260