Only show taxonomy sidebar when tagged to a live taxon

The recent changes to the taxonomy exposed that we have duplicated
logic between this application and the components. At the moment this
app thinks that there are taxons, so it tries to show the sidebar.
However, the `govuk_component/taxonomy_sidebar` component *doesn't*
think there are taxons, because it only looks at the live ones.

This is a temporary fix, we will re-architect this so that the logic is
simple and in only one place.

app/models/navigation_type.rb

@@ -8,14 +8,14 @@ def initialize(content_item)
 
   def should_present_taxonomy_navigation?
     !content_is_tagged_to_browse_pages? &&
-      content_is_tagged_to_a_taxon? &&
+      content_is_tagged_to_a_live_taxon? &&
       content_schema_is_guidance?
   end
 
 private
 
-  def content_is_tagged_to_a_taxon?
-    @content_item.dig("links", "taxons").present?
+  def content_is_tagged_to_a_live_taxon?
+    @content_item.dig("links", "taxons").to_a.any? { |taxon| taxon["phase"] == "live" }
   end
 
   def content_is_tagged_to_browse_pages?