Remove manual capacity management.

src/Avalonia.Styling/StyledElement.cs

@@ -207,7 +207,7 @@ namespace Avalonia
         /// </remarks>
         public Styles Styles
         {
-            get 
+            get
             {
                 if (_styles is null)
                 {
@@ -860,8 +860,6 @@ namespace Avalonia
         {
             var count = styles.Count;
 
-            result.Capacity += count;
-
             for (var i = 0; i < count; ++i)
             {
                 var style = styles[i];