Fix binding redirect in test.

Author: grokys

test/GitHub.App.UnitTests/app.config

@@ -3,7 +3,7 @@
     <assemblyBinding xmlns="urn:schemas-microsoft-com:asm.v1">
       <dependentAssembly>
         <assemblyIdentity name="Newtonsoft.Json" publicKeyToken="30AD4FE6B2A6AEED" culture="neutral"/>
-        <bindingRedirect oldVersion="0.0.0.0-6.0.0.0" newVersion="10.0.0.0"/>
+        <bindingRedirect oldVersion="0.0.0.0-6.0.0.0" newVersion="9.0.0.0"/>
       </dependentAssembly>
     </assemblyBinding>
   </runtime>