Update error message text when 2.0 SDK is required to build a project

Author: dsplaisted

src/Tasks/Common/Resources/Strings.resx

@@ -313,6 +313,6 @@
     <value>Resolved file has a bad image, no metadata, or is otherwise inaccessible. {0}</value>
   </data>
   <data name="UnsupportedSDKVersionForNetStandard20" xml:space="preserve">
-    <value>The version of Microsoft.NET.Sdk used by this project is insufficient to support .NET Standard 2.0 which is required by this project's references.  Please install version 2.0 or higher of the .NET Core SDK.</value>
+    <value>The version of Microsoft.NET.Sdk used by this project is insufficient to support references to libraries targeting .NET Standard 1.5 or higher.  Please install version 2.0 or higher of the .NET Core SDK.</value>
   </data>
 </root>