Revert "Update ConnectionMultiplexer.cs"

This reverts commit 2e545863.

StackExchange.Redis/StackExchange/Redis/ConnectionMultiplexer.cs

@@ -10,11 +10,11 @@
 using System.Threading;
 using System.Threading.Tasks;
 using System.Collections.Concurrent;
-using System.Runtime;
 #if NET40
 using Microsoft.Runtime.CompilerServices;
 #else
 using System.Runtime.CompilerServices;
+using System.Runtime;
 #endif
 
 namespace StackExchange.Redis