chore: remove unused portfinder dependency
chore: remove unused portfinder dependency

The portfinder dependency appears to be unused. It is the lone source
of an npm audit warning on end-user installation. This change removes
it.

dherault/serverless-offline,dherault/serverless-offline,dherault/serverless-offline,dherault/serverless-offline,dherault/serverless-offline,dherault/serverless-offline,dherault/serverless-offline