blade: Fix incorrect texture format (zed-industries#10524)

Fixes image rendering
Closes zed-industries#10505

Before:

![image](https://github.com/zed-industries/zed/assets/71973804/3a903279-d631-4ca6-9f46-3065c7ed3073)


After:

![image](https://github.com/zed-industries/zed/assets/71973804/ab3a73e5-bf21-4df7-a9c1-a74bd1993a5b)


Release Notes:

- N/A

crates/gpui/src/platform/blade/blade_atlas.rs

@@ -162,7 +162,7 @@ impl BladeAtlasState {
                 usage = gpu::TextureUsage::COPY | gpu::TextureUsage::RESOURCE;
             }
             AtlasTextureKind::Polychrome => {
-                format = gpu::TextureFormat::Rgba8Unorm;
+                format = gpu::TextureFormat::Bgra8Unorm;
                 usage = gpu::TextureUsage::COPY | gpu::TextureUsage::RESOURCE;
             }
             AtlasTextureKind::Path => {