Remove internal notes from specialist document presenter

Certain Specilialist Documents can have internal notes that
should not be presented on the frontend.

app/presenters/specialist_document_presenter.rb

@@ -127,6 +127,7 @@ def sorted_facets_with_values
     facets
       .select { |f| facet_values[f["key"]] && facet_values[f["key"]].present? }
       .reject { |f| f["key"] == first_published_at_facet_key }
+      .reject { |f| f["key"] == internal_notes_facet_key }
       .sort_by { |f| f["type"] }
   end
 
@@ -181,6 +182,10 @@ def first_published_at_facet_key
     "first_published_at"
   end
 
+  def internal_notes_facet_key
+    "internal_notes"
+  end
+
   # first_published_at does not have reliable data
   # at time of writing dates could be after public_updated_at
   # details.first_public_at is not provided