The mkcert CA certificate is now persistently stored on your system. There is no real downside to keeping it and chances are you are going to be using it again at some point in the near future since mkcert is now the only real solution to creating HTTPS certificates for testing and development purposes. Also, the
localhost.p12 certificate that your server is now using will only continue to work while the mkcert CA certificate is installed.
If you do decide that you want to remove the mkcert CA certificate from your computer then run the following command in a terminal from the <> folder:
$env:CAROOT = pwd; $env:TRUST_STORES = 'system'; .\mkcert.exe -uninstall
CAROOT=$(pwd) TRUST_STORES=system ./mkcert -uninstall
CAROOT=$(pwd) TRUST_STORES=system,nss ./mkcert -uninstall