toolkit latest is deprecated, mention default instead (#2776)

- in `using-directives.md`

website/docs/guides/introduction/using-directives.md

@@ -142,5 +142,5 @@ Directives with a test scope equivalent:
 //> using test.javaProp foo1=bar1
 //> using test.option -Xfatal-warnings
 //> using test.resourceDir testResources
-//> using test.toolkit latest
+//> using test.toolkit default
 ```