refactor(code-server): drop Codex access token

No longer used; removes the CODEX_ACCESS_TOKEN variable from the service
definition and its example env file.

code-server/.env.example

@@ -11,6 +11,3 @@ PASSWORD=
 # Git identity baked into the container (author + committer).
 GIT_NAME=
 GIT_EMAIL=
-
-# OpenAI Codex CLI auth token. Leave blank if you don't use Codex.
-CODEX_ACCESS_TOKEN=