Delete MefV1HostServices.Default.

This API was left in by accident from the portable MEF switch. It creates a container that is empty since it's looking for MEFv1 attributes in a MEFv2 assembly. Any use of the resulting HostServices will just fail.

CR: mavasani; jaredpar (changeset 1385133)

Src/Workspaces/Core/Desktop/Workspace/Host/Mef/MefV1HostServices.cs

@@ -122,24 +122,5 @@ public override int GetHashCode()
                 return Hash.Combine(this.MetadataTypeName.GetHashCode(), this.ExtensionTypeName.GetHashCode());
             }
         }
-
-        #region Defaults
-        private static MefV1HostServices defaultHost;
-
-        public static MefV1HostServices DefaultHost
-        {
-            get
-            {
-                if (defaultHost == null)
-                {
-                    var host = MefV1HostServices.Create(MefHostServices.DefaultAssemblies);
-                    Interlocked.CompareExchange(ref defaultHost, host, null);
-                }
-
-                return defaultHost;
-            }
-        }
-
-        #endregion
     }
 }
\ No newline at end of file