Fix docstring.

Author: maxvoxel8

src/ImageSharp.Drawing/Processing/PathGradientBrush.cs

@@ -230,6 +230,7 @@ private class PathGradientBrushApplicator<TPixel> : BrushApplicator<TPixel>
             /// <param name="source">The source image.</param>
             /// <param name="edges">Edges of the polygon.</param>
             /// <param name="centerColor">Color at the center of the gradient area to which the other colors converge.</param>
+            /// <param name="hasSpecialCenterColor">Whether the center color is different from a smooth gradient between the edges.</param>
             public PathGradientBrushApplicator(
                 Configuration configuration,
                 GraphicsOptions options,