Do not clear relationships on destroy

Co-authored-by: Mary Lee <mary.lee@hashrocket.com>
Co-authored-by: Gabriel Reis <gabriel@hashrocket.com>

Author: 3 people

lib/json_api_client/resource.rb

@@ -463,7 +463,6 @@ def destroy
         false
       else
         mark_as_destroyed!
-        self.relationships.attributes.clear
         self.relationships.last_result_set = nil
         _clear_cached_relationships
         true