[REFACTOR] Make EtdFileSetPresenter agnostic about underlying hash

**RATIONALE**
We don't want the presenter to have to know details about the
uderlying SolrDocument implementation like attribute suffixes.

app/models/solr_document.rb

@@ -108,6 +108,10 @@ def partnering_agency
     self[Solrizer.solr_name('partnering_agency')]
   end
 
+  def pcdm_use
+    self[Solrizer.solr_name('pcdm_use')]&.first
+  end
+
   def submitting_type
     self[Solrizer.solr_name('submitting_type')]
   end

app/presenters/etd_file_set_presenter.rb

@@ -4,11 +4,7 @@ class EtdFileSetPresenter < Hyrax::FileSetPresenter
            to: :solr_document
 
   def primary?
-    solr_document.fetch("pcdm_use_tesim", []).include?("primary")
-  end
-
-  def supplementary?
-    !primary?
+    pcdm_use == "primary"
   end
 
   def permission_badge