Update JSON.Net redirects in SampleWebJob after recent dependabot update (#203).

Author: StephenMolloy

samples/SampleWebJob/app.config

@@ -42,7 +42,7 @@
       </dependentAssembly>
       <dependentAssembly>
         <assemblyIdentity name="Newtonsoft.Json" publicKeyToken="30ad4fe6b2a6aeed" culture="neutral" />
-        <bindingRedirect oldVersion="0.0.0.0-12.0.0.0" newVersion="12.0.0.0" />
+        <bindingRedirect oldVersion="0.0.0.0-13.0.0.0" newVersion="13.0.0.0" />
       </dependentAssembly>
     </assemblyBinding>
   </runtime>