Remove circleci checks for Node < 20 to unblock fastify 5

The fastify v5 PR is blocked by the Node < 20 checks not being run. These checks have been removed on that branch because Fastify v5 requires Node 20+

Author: xzyfer

.circleci/config.yml

@@ -79,7 +79,5 @@ workflows:
           matrix:
             parameters:
               node-version:
-                - "16"
-                - "18"
                 - "20"
       - Incremental Delivery