monaco_editor: use default multiCursorModifier
This was a workaround for ChromeOS, but we realized it was not really good. Disable it for the same reasons as slapos!1196 (merged) :
- not everybody use ChromeOS
- this breaks the ctrl+click shortcut to go to definition/follow link
- it makes ERP5 monaco editor behaves differently from others monaco editor
- ChromeOS users can use chrome://flags/#use-search-click-for-right-click