removing xunit.extensibility.core from list of packages

Author: mumou

src/ServiceManagement/HDInsight/Commands.HDInsight.Test/packages.config

@@ -26,6 +26,5 @@
   <package id="xunit.abstractions" version="2.0.0" targetFramework="net45" />
   <package id="xunit.assert" version="2.1.0-beta1-build2945" targetFramework="net45" />
   <package id="xunit.core" version="2.1.0-beta1-build2945" targetFramework="net45" />
-  <package id="xunit.extensibility.core" version="2.1.0-beta1-build2945" targetFramework="net45" />
   <package id="xunit.runner.visualstudio" version="2.1.0-beta1-build1051" targetFramework="net45" />
 </packages>