[Schema Inaccuracy]  `/repos/{owner}/{repo}/pulls/comments/{comment_id}` actually has nullable `user`

# Schema Inaccuracy

Pull Requests comments claim to have a non-nullable `user` (the field is marked as "required") yet this field is actually nullable.

## Expected

The field `user` should not be marked as required.

## Reproduction Steps

`/repos/ocaml/ocaml/pulls/comments/1758736814` which has:

```
...
  "user": null,
...
```


