consistently use stdlib::ensure_packages()

In b608826 ewoud already introduced
`stdlib::ensure_packages()`. There's another place that used the legacy
`ensure_packages()` function. It's deprecated since stdlib 9. This
commit updates the old code to also use `stdlib::ensure_packages()`

manifests/server/install.pp

@@ -11,7 +11,7 @@
   }
 
   if $puppet::server::git_repo {
-    ensure_packages(['git'])
+    stdlib::ensure_packages(['git'])
   }
 
   if $puppet::server::manage_user {