Remove System.* as NuGet references

Author: asbjornu

src/GitVersionTask.Tests/packages.config

@@ -18,21 +18,4 @@
   <package id="NUnitTestAdapter" version="2.0.0" targetFramework="net45" />
   <package id="ObjectApproval" version="1.3.0" targetFramework="net45" />
   <package id="Shouldly" version="2.7.0" targetFramework="net45" />
-  <package id="System.Collections" version="4.0.0" targetFramework="net45" />
-  <package id="System.Collections.Immutable" version="1.1.37" targetFramework="net45" />
-  <package id="System.Diagnostics.Debug" version="4.0.0" targetFramework="net45" />
-  <package id="System.Globalization" version="4.0.0" targetFramework="net45" />
-  <package id="System.IO" version="4.0.0" targetFramework="net45" />
-  <package id="System.Linq" version="4.0.0" targetFramework="net45" />
-  <package id="System.Reflection" version="4.0.0" targetFramework="net45" />
-  <package id="System.Reflection.Extensions" version="4.0.0" targetFramework="net45" />
-  <package id="System.Reflection.Metadata" version="1.0.22" targetFramework="net45" />
-  <package id="System.Reflection.Primitives" version="4.0.0" targetFramework="net45" />
-  <package id="System.Resources.ResourceManager" version="4.0.0" targetFramework="net45" />
-  <package id="System.Runtime" version="4.0.0" targetFramework="net45" />
-  <package id="System.Runtime.Extensions" version="4.0.0" targetFramework="net45" />
-  <package id="System.Runtime.InteropServices" version="4.0.0" targetFramework="net45" />
-  <package id="System.Text.Encoding" version="4.0.0" targetFramework="net45" />
-  <package id="System.Text.Encoding.Extensions" version="4.0.0" targetFramework="net45" />
-  <package id="System.Threading" version="4.0.0" targetFramework="net45" />
 </packages>