🐛 Restore qt: 'standard' to SolrService

In `ActiveFedora::SolrService` we always assign the `qt: 'standard'`.[1]

However, with [this old commit][1] we dropped passing the `qt:
'standard'` when we had `use_valkyrie` of true.

We discovered this bug when upgrading Hyku and Bulkrax to Hyrax v3.x and
some.

Closes #6676

Related to:

- #3857

[1]:https://github.com/samvera/active_fedora/blob/8e7d365a087974b4ff9b9217f792c0c049789de6/lib/active_fedora/solr_service.rb#L40-L48
[2]:be6104f

app/services/hyrax/solr_service.rb

@@ -48,7 +48,7 @@ def get(query = nil, **args)
       solr_path = args.delete(:path) || Hyrax.config.solr_select_path
       args = args.merge(q: query) if query.present?
 
-      args = args.merge(qt: 'standard') unless query.blank? || use_valkyrie
+      args = args.merge(qt: 'standard') if query.present?
       connection.get(solr_path, params: args)
     end
 
@@ -68,7 +68,7 @@ def post(query = nil, **args)
       solr_path = args.delete(:path) || Hyrax.config.solr_select_path
       args = args.merge(q: query) if query.present?
 
-      args = args.merge(qt: 'standard') unless query.blank? || use_valkyrie
+      args = args.merge(qt: 'standard') if query.present?
       connection.post(solr_path, data: args)
     end