(build) Switch to package hosted on Azure Artifacts

MyGet appears to be down, and as a result, we can't run the build :-(

Author: gep13

build.cake

@@ -2,7 +2,7 @@
 // Tools
 ///////////////////////////////////////////////////////////////////////////////
 
-#tool dotnet:https://www.myget.org/F/cake-contrib/api/v3/index.json?package=KuduSync.Tool&version=1.5.4-g3916ad7218
+#tool dotnet:https://pkgs.dev.azure.com/cake-contrib/Home/_packaging/addins/nuget/v3/index.json?package=KuduSync.Tool&version=1.5.4-g13cb5857b6
 
 ///////////////////////////////////////////////////////////////////////////////
 // Addins