MemberSearchBuilder does not need collection from the scope

The collection id is already passed to the search builder as parameters.
This loosens the coupling between the search builder and the controller.

app/search_builders/curation_concerns/member_search_builder.rb

@@ -6,12 +6,16 @@ class MemberSearchBuilder < ::SearchBuilder
     # Defines which search_params_logic should be used when searching for Collection members
     self.default_processor_chain += [:include_collection_ids]
 
-    delegate :collection, to: :scope
-
     # include filters into the query to only include the collection memebers
     def include_collection_ids(solr_parameters)
       solr_parameters[:fq] ||= []
-      solr_parameters[:fq] << "{!join from=#{from_field} to=id}id:#{collection.id}"
+      solr_parameters[:fq] << "{!join from=#{from_field} to=id}id:#{collection_id}"
     end
+
+    protected
+
+      def collection_id
+        blacklight_params.fetch('id')
+      end
   end
 end