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

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### Hardware Info

_No response_

首先检查 issue #1670 中引用的更改以及 Preferences → Interface 字体设置。确认默认文档字体或等宽字体在哪里被选中，然后验证 Code 默认使用等宽字体打开，同时该偏好设置仍然可用。

由索引模型根据 Issue 内容生成。