Cleanup and update references.

src/ImageSharp/Processing/Processors/Quantization/EuclideanPixelMap{TPixel}.cs

@@ -2,12 +2,10 @@
 // Licensed under the Apache License, Version 2.0.
 
 using System;
-using System.Buffers;
 using System.Collections.Concurrent;
 using System.Numerics;
 using System.Runtime.CompilerServices;
 using System.Runtime.InteropServices;
-using SixLabors.ImageSharp.Memory;
 using SixLabors.ImageSharp.PixelFormats;
 
 namespace SixLabors.ImageSharp.Processing.Processors.Quantization
@@ -106,5 +104,5 @@ namespace SixLabors.ImageSharp.Processing.Processors.Quantization
             match = Unsafe.Add(ref paletteRef, index);
             return index;
         }
-        }
+    }
 }

src/ImageSharp/Processing/Processors/Quantization/FrameQuantizerExtensions.cs

@@ -3,7 +3,6 @@
 
 using System;
 using System.Runtime.CompilerServices;
-using System.Runtime.InteropServices;
 using SixLabors.ImageSharp.Advanced;
 using SixLabors.ImageSharp.Memory;
 using SixLabors.ImageSharp.PixelFormats;

src/ImageSharp/Processing/Processors/Quantization/PaletteFrameQuantizer{TPixel}.cs

@@ -2,10 +2,7 @@
 // Licensed under the Apache License, Version 2.0.
 
 using System;
-using System.Buffers;
 using System.Runtime.CompilerServices;
-using System.Runtime.InteropServices;
-using SixLabors.ImageSharp.Memory;
 using SixLabors.ImageSharp.PixelFormats;
 
 namespace SixLabors.ImageSharp.Processing.Processors.Quantization

src/ImageSharp/Processing/Processors/Quantization/PaletteQuantizer.cs

@@ -56,7 +56,9 @@ namespace SixLabors.ImageSharp.Processing.Processors.Quantization
             // multi frame gifs using a global palette.
             int length = Math.Min(this.colorPalette.Length, options.MaxColors);
             var palette = new TPixel[length];
+
             Color.ToPixel(configuration, this.colorPalette.Span, palette.AsSpan());
+
             var pixelMap = new EuclideanPixelMap<TPixel>(configuration, palette, length);
             return new PaletteFrameQuantizer<TPixel>(configuration, options, pixelMap);
         }

tests/Images/External

@@ -1 +1 @@
-Subproject commit f8a76fd3a900b90c98df67ac896574383a4d09f3
+Subproject commit 1fea1ceab89e87cc5f11376fa46164d3d27566c0