Gizmos::line() with a transparent color display weird

## Bevy version
0.13.2

## Content

I called `Gizmos#line()` with a transparent white color.

```rust
#[derive(Resource, Clone, Reflect)]
pub struct EditModeConfig {
pub weak_lines_color: Color,
pub lines_color: Color,
pub hlt_lines_color: Color,
pub hlt_rect_move_speed: f32,
}
impl Default for EditModeConfig {
fn default() -> Self {
Self {
weak_lines_color: Color::rgba_linear(1., 1., 1., 0.06),
// I tried both rgba() and rgba_linear(), neither works
lines_color: Color::rgba_linear(1., 1., 1., 0.3),
hlt_lines_color: Color::rgba_linear(1., 1., 1., 0.5),
hlt_rect_move_speed: 15.0,
}
}
}
```
It displayed like this. These lines were not transparent.

---

But after I clicked this button in bevy-inspector-egui's color panel, lines displayed correctly.

Start by reproducing the reported Gizmos#line() behavior on Bevy 0.13.2 using the transparent Color::rgba_linear values shown in the issue, then compare it with the result after the bevy-inspector-egui color-panel interaction. Done means transparent line colors render with the expected opacity, with a regression test covering the behavior.

Written by the indexing model from the issue text.