Fix B4G4R4A4_UNORM swizzle with the Metal GPU driver

src/gpu/metal/SDL_gpu_metal.m

@@ -1434,10 +1434,10 @@ static MetalTexture *METAL_INTERNAL_CreateTexture(
     // This format isn't natively supported so let's swizzle!
     if (createinfo->format == SDL_GPU_TEXTUREFORMAT_B4G4R4A4_UNORM) {
         if (@available(macOS 10.15, iOS 13.0, tvOS 13.0, *)) {
-            textureDescriptor.swizzle = MTLTextureSwizzleChannelsMake(MTLTextureSwizzleBlue,
-                                                                      MTLTextureSwizzleGreen,
-                                                                      MTLTextureSwizzleRed,
-                                                                      MTLTextureSwizzleAlpha);
+            textureDescriptor.swizzle = MTLTextureSwizzleChannelsMake(MTLTextureSwizzleGreen,
+                                                                      MTLTextureSwizzleBlue,
+                                                                      MTLTextureSwizzleAlpha,
+                                                                      MTLTextureSwizzleRed);
         } else {
             SET_STRING_ERROR_AND_RETURN("SDL_GPU_TEXTUREFORMAT_B4G4R4A4_UNORM is not supported", NULL);
         }