Update src/ImageSharp/Formats/Webp/Lossless/HistogramEncoder.cs

Co-authored-by: Anton Firszov <antonfir@gmail.com>

Author: JimBobSquarePants

src/ImageSharp/Formats/Webp/Lossless/HistogramEncoder.cs

@@ -383,8 +383,7 @@ private static bool HistogramCombineStochastic(Vp8LHistogramSet histograms, int
                 idx2 = mappings[idx2];
 
                 // Calculate cost reduction on combination.
-                double currCost = 0;
-                currCost = HistoPriorityListPush(histoPriorityList, maxSize, histograms, idx1, idx2, bestCost, stats, bitsEntropy);
+                double currCost = HistoPriorityListPush(histoPriorityList, maxSize, histograms, idx1, idx2, bestCost, stats, bitsEntropy);
 
                 // Found a better pair?
                 if (currCost < 0)