Code uses system document font instead of monospace font by default

### What Happened?

in #1670 Code was changed to use the document font instead of the monospace font.

### Steps to Reproduce

1. Open preferences → Interface
2. See that system font is Open Sans, not Roboto Mono

### Expected Behavior

Document font is for apps like Evince. Monospace font is what Code should use.

### OS Version

8.x (Circe)

### OS Architecture

amd64 (on most hardwares)

### Session Type

Secure Session (Wayland, This is the default)

### Software Version

Latest release (I have run all updates)

### Log Output

```shell

```

### Hardware Info

_No response_