Graphite: Fixed issue with functions with multiple required params and no defaults caused params that could not be edited (groupByNodes groupByTags) (#21814)

* Graphite: Fixed issue functions with multiple required params and no defaults

* removed some prev changes

* Update public/app/plugins/datasource/graphite/func_editor.ts

Co-authored-by: Dominik Prokop <dominik.prokop@grafana.com>