Please update mikrotik instructions

According to the following post in the mikrotik forums...

https://forum.mikrotik.com/t/simple-question-adding-nextdns-servers-and-disabling-default-dynamic-servers/272416/2

It is no longer needed to download and install all the certificates. Default certificate for NextDNS is already contained within the ROS7. This allows you to remove the first two lines of the Mikrotik router instrcutions and simplify them.