Stable Tag no longer default

[avatarworf]

dotcom-tool-kit/plugins/circleci/src/circleci-config.ts

Line 169 in 1934be7

docker: [{ image: 'cimg/base:stable' }],

per: https://circleci.com/developer/images/image/cimg/base#image-tags

current - This image tag points to the latest, production ready base image. This is a replacement for the old stable tag. This image should be used by projects that want a decent level of stability but would like to get occasional software updates. It is typically updated once a month.