Removed unused usings.

Author: tillig

src/Autofac/Features/Collections/CollectionRegistrationSource.cs

@@ -2,8 +2,6 @@
 // Licensed under the MIT License. See LICENSE in the project root for license information.
 
 using System.Collections;
-using System.Collections.Generic;
-using System.Linq;
 using System.Linq.Expressions;
 using System.Reflection;
 using System.Runtime.CompilerServices;