Update to new CI pkg domain

Author: kzu

src/nuget.config

@@ -7,7 +7,7 @@
   <packageSources>
     <clear />
     <add key="nuget.org" value="https://api.nuget.org/v3/index.json" />
-    <add key="kzu.io" value="https://pkg.kzu.io/index.json" />
+    <add key="kzu.io" value="https://pkg.kzu.app/index.json" />
   </packageSources>  
   <trustedSigners>
     <author name="Microsoft">