Remove unnecessary Clear() and scratch buffer

src/ImageSharp/Formats/Webp/Lossy/LossyUtils.cs

@@ -127,7 +127,7 @@ namespace SixLabors.ImageSharp.Formats.Webp.Lossy
 #if SUPPORTS_RUNTIME_INTRINSICS
             if (Sse41.IsSupported)
             {
-                int diffSum = TTransformSse41(a, b, w, scratch);
+                int diffSum = TTransformSse41(a, b, w);
                 return Math.Abs(diffSum) >> 5;
             }
             else
@@ -654,7 +654,7 @@ namespace SixLabors.ImageSharp.Formats.Webp.Lossy
         /// Returns the weighted sum of the absolute value of transformed coefficients.
         /// w[] contains a row-major 4 by 4 symmetric matrix.
         /// </summary>
-        public static int TTransformSse41(Span<byte> inputA, Span<byte> inputB, Span<ushort> w, Span<int> scratch)
+        public static int TTransformSse41(Span<byte> inputA, Span<byte> inputB, Span<ushort> w)
         {
             // Load and combine inputs.
             Vector128<byte> ina0 = Unsafe.As<byte, Vector128<byte>>(ref MemoryMarshal.GetReference(inputA));

src/ImageSharp/Formats/Webp/Lossy/Vp8Histogram.cs

@@ -49,7 +49,6 @@ namespace SixLabors.ImageSharp.Formats.Webp.Lossy
             this.distribution.AsSpan().Clear();
             for (j = startBlock; j < endBlock; j++)
             {
-                this.output.AsSpan().Clear();
                 this.Vp8FTransform(reference.Slice(WebpLookupTables.Vp8DspScan[j]), pred.Slice(WebpLookupTables.Vp8DspScan[j]), this.output);
 
                 // Convert coefficients to bin.