Build/Test Tools: Bump the Node.js version for Codespaces.

This bumps the version of Node.js used in GitHub Codespaces from 16 to 20.

Follow up to [57212].

Props itschristiandale, huzaifaalmesbah.
Fixes #60555.

git-svn-id: https://develop.svn.wordpress.org/trunk@57667 602fd350-edb4-49c9-b593-d223f7449a82

.devcontainer/devcontainer.json

@@ -11,7 +11,7 @@
             "username": "wordpress"
         },
         "ghcr.io/devcontainers/features/node:1": {
-            "version": "16"
+            "version": "20"
         },
         "ghcr.io/devcontainers/features/docker-in-docker:2": {},
         "ghcr.io/devcontainers/features/git:1": {}