Updated the validateSettings method to check stripe_plans
Updated the validateSettings method to check stripe_plans

refs #11765

This ensures that plans will always be set to 1 of the currency

bitjson/Ghost,TryGhost/Ghost,e10/Ghost,janvt/Ghost,ErisDS/Ghost,janvt/Ghost,JohnONolan/Ghost,ErisDS/Ghost,JohnONolan/Ghost,TryGhost/Ghost,bitjson/Ghost,ErisDS/Ghost,JohnONolan/Ghost,TryGhost/Ghost,e10/Ghost