Remove certain holidays from calendar

You cannot. You do not have the ability to edit events on a subscribed calendar. You can either unsubscribe to the one you are currently using and subscribe to another, or you can create your own holiday calendar, or you can subscribe to one that better meets your needs.

You can not edit a subscribed calendar. The default holiday calendar contains holidays for a number of religions. If it doesn't suit your needs, unsubscribe from it and subscribe to one that does meet your needs.