IndexBuilder.SingleTable: Remove .ToList(), no need for enumeration

Even in case when we need to copy refs to some collection we don't need it,
Reverse() copies refs to a buffer collection anyway.

Author: alex-kulakov

Orm/Xtensive.Orm/Orm/Building/Builders/IndexBuilder.SingleTable.cs

@@ -79,15 +79,14 @@ private void BuildSingleTableIndexes(TypeInfo type)
       if (!type.IsAbstract)
         primaryIndexFilterTypes.Add(type);
       primaryIndexFilterTypes.AddRange(descendants);
-      
+
       // Import inherited indexes
       var ancestorIndexes = root.Indexes
         .Where(i => types.Contains(i.ReflectedType) && !i.IsTyped)
         .Reverse()
         .Select(i => untypedIndexes.Contains(i)
           ? root.Indexes.Single(index => index.DeclaringIndex == i.DeclaringIndex && index.ReflectedType == type && index.IsTyped)
-          : i)
-        .ToList();
+          : i);
       foreach (var ancestorIndex in ancestorIndexes) {
         if (type.Indexes.Any(i => 
             i.DeclaringIndex == ancestorIndex.DeclaringIndex &&