Intepret glTF colors as linear instead of sRGB (#6828)

# Objective

Fixes #6827

## Solution

Use the `Color::rgba_linear` function instead of the `Color::rgba` function to correctly interpret colors from glTF files in the linear color space rather than the incorrect sRGB color space

Author: BigWingBeat

crates/bevy_gltf/src/loader.rs

@@ -669,7 +669,7 @@ fn load_material(material: &Material, load_context: &mut LoadContext) -> Handle<
     load_context.set_labeled_asset(
         &material_label,
         LoadedAsset::new(StandardMaterial {
-            base_color: Color::rgba(color[0], color[1], color[2], color[3]),
+            base_color: Color::rgba_linear(color[0], color[1], color[2], color[3]),
             base_color_texture,
             perceptual_roughness: pbr.roughness_factor(),
             metallic: pbr.metallic_factor(),
@@ -682,7 +682,7 @@ fn load_material(material: &Material, load_context: &mut LoadContext) -> Handle<
                 Some(Face::Back)
             },
             occlusion_texture,
-            emissive: Color::rgba(emissive[0], emissive[1], emissive[2], 1.0),
+            emissive: Color::rgb_linear(emissive[0], emissive[1], emissive[2]),
             emissive_texture,
             unlit: material.unlit(),
             alpha_mode: alpha_mode(material),