fixes(Doc): fixes AvaloniaList XML Comments

src/Avalonia.Base/Collections/AvaloniaList.cs

@@ -280,8 +280,8 @@ namespace Avalonia.Collections
         /// <summary>
         /// Gets a range of items from the collection.
         /// </summary>
-        /// <param name="index">The first index to remove.</param>
-        /// <param name="count">The number of items to remove.</param>
+        /// <param name="index">The zero-based <see cref="AvaloniaList{T}"/> index at which the range starts.</param>
+        /// <param name="count">The number of elements in the range.</param>
         public IEnumerable<T> GetRange(int index, int count)
         {
             return _inner.GetRange(index, count);
@@ -455,7 +455,7 @@ namespace Avalonia.Collections
         }
 
         /// <summary>
-        /// Ensures that the capacity of the list is at least <see cref="capacity"/>.
+        /// Ensures that the capacity of the list is at least <see cref="Capacity"/>.
         /// </summary>
         /// <param name="capacity">The capacity.</param>
         public void EnsureCapacity(int capacity)