Removing no-longer-used error code

Author: benrr101

src/Microsoft.Data.SqlClient/src/Microsoft/Data/Common/AdapterUtil.cs

@@ -945,7 +945,7 @@ internal enum InternalErrorCode
 
             SqlDependencyObtainProcessDispatcherFailureObjectHandle = 50,
             SqlDependencyProcessDispatcherFailureCreateInstance = 51,
-            SqlDependencyProcessDispatcherFailureAppDomain = 52,
+            
             SqlDependencyCommandHashIsNotAssociatedWithNotification = 53,
 
             UnknownTransactionFailure = 60,