Removing unused field in HistoryView

Author: StanleyGoldman

src/UnityExtension/Assets/Editor/GitHub.Unity/UI/HistoryView.cs

@@ -37,7 +37,6 @@ class HistoryView : Subview
 
         [NonSerialized] private int historyStartIndex;
         [NonSerialized] private int historyStopIndex;
-        [NonSerialized] private float lastWidth;
         [NonSerialized] private int listID;
         [NonSerialized] private int newSelectionIndex;
         [NonSerialized] private float scrollOffset;