refactor: comment out optional env vars in diun and code-server

code-server/.env.example

@@ -15,3 +15,6 @@ GIT_EMAIL=
 # Container hostname, also passed in as HOST -- the name zsh's prompt shows.
 # Not named HOSTNAME: the deploying shell's own HOSTNAME would override it.
 SERVICE_HOSTNAME=code-server
+
+# Name of the installed web app.
+# PWA_APPNAME=code-server