perf: drop unused select_related("owner") from email_documents

The permission check loop that used to call has_perms_owner_aware()
(which read .owner) was already replaced with permitted_document_ids()
resolved once into a set. No other code in email_documents touches
.owner, so the select_related is dead weight.

src/documents/views.py

@@ -1929,7 +1929,7 @@ class DocumentViewSet(
         message = validated_data.get("message")
         use_archive_version = validated_data.get("use_archive_version", True)
 
-        documents = Document.objects.select_related("owner").filter(pk__in=document_ids)
+        documents = Document.objects.filter(pk__in=document_ids)
         if request.user is not None:
             permitted_ids = set(permitted_document_ids(request.user))
             if not all(document.pk in permitted_ids for document in documents):