fix: Fix ColorTableMode parameter of Gif encoder in release build

In the release build, the GifEncoder.ColorTableMode property in the ImageSharp library has been renamed to FrameColorTableMode. This change ensures the code compiles correctly and generates GIF images under the release configuration.

Author: Yushu2606

src/Utils/ServerStreamWriterExtensions.cs

@@ -2,6 +2,7 @@
 using Grpc.Core;
 using SixLabors.ImageSharp;
 #if RELEASE
+using SixLabors.ImageSharp.Formats;
 using SixLabors.ImageSharp.Formats.Gif;
 using SixLabors.ImageSharp.Processing;
 #endif
@@ -35,7 +36,7 @@ internal async Task WriteToResponseAsync(Image image, bool isAnime)
                 GifEncoder encoder = new()
                 {
                     Quantizer = KnownQuantizers.Wu,
-                    ColorTableMode = GifColorTableMode.Local
+                    ColorTableMode = FrameColorTableMode.Local
                 };
                 await image.SaveAsGifAsync(outStream, encoder);
             }