Code indentation breaks out of column

Placing a `Ui::code` directly in a `Ui::columns` results in indented lines breaking the layout and sticking out of the column:


Wrapping the column content in a `vertical` apparently fixes this. I'm still opening this issue since this doesn't seem like something that should be happening. Note that the same happens with `Ui::monospace`, I just chose `code` for my example because the background makes it easier to see what's going on.

**To Reproduce**
Execute the following code against either the latest version of eframe (0.31.1) or master.

```rust
use eframe::::egui;

fn main() {
eframe::run_simple_native(
"repro",
eframe::NativeOptions::default(),
move |ctx, _frame| {
egui::CentralPanel::default().show(ctx, |ui| {
ui.columns(2, |columns| {
columns[1].code(
r#"
Line1 has no indentation
Line2 has some indentation
"#
.trim(),
)
});
});
},
);
}
```

Start by running the provided eframe reproducer and inspect the egui Ui::columns, Ui::code, and Ui::monospace entry points involved in the layout. The issue is done when indented code remains within its column without requiring a vertical wrapper, with regression coverage for the reproduced case.

Written by the indexing model from the issue text.