[Edit docs] page text is incorrect

[wileyj]

URL of the page to change: https://docs.stacks.co/nakamoto-upgrade/setting-up-a-primary-post-nakamoto-testnet-node

this is describing primary testnet, not nakamoto testnet (i don't see nakamoto testnet in the docs anywhere else, at least not a config that may be used).

tagging @kenrogers , else i'll address in a PR later