CircleCI uses end-of-life Node.js 16 alongside Node.js 21

[Mike McCready]

Issue description

The CircleCI workflow .circleci/config.yml is using a mixture of Node.js 16 and 21 environments to test. See CircleCI pipeline.

Since Node.js 16 is now end-of-life it should no longer be used.

The previous update to parts of the workflow moving it to Node.js 20 was initiated by Renovate without regard to using a consistent version of Node.js throughout the workflow.

Currently used versions

code-coverage/.circleci/config.yml

Lines 11 to 12 in ced661d

 docker: 
   - image: cimg/node:21.4.0 

code-coverage/.circleci/config.yml

Lines 43 to 44 in 62bfef2

 name: Install node 16 
 command: nvm install 16.16.0 

code-coverage/.circleci/config.yml

Lines 89 to 90 in 62bfef2

 docker: 
   - image: cypress/base:16.18.1 

Suggestion

The CircleCI workflow .circleci/config.yml should use consistent versions of Node.js based on Node.js 20 throughout.