editor_css_path and editor_css_selectors removed from core in 3.0

[Mark-H]

Per modxcms/revolution#14843, the editor_css_path and editor_css_selectors system settings will be removed from the core in 3.0. It appears the TinyMCE package still (potentially) uses that, so it is my opinion that TinyMCE should be updated to use a setting from its own namespace.

[Mark-H]

Same with fe_editor_lang in modxcms/revolution#14848