Remove reference to COMPOSER_IGNORE_XDEBUG_WARN

doc/03-cli.md

@@ -858,10 +858,6 @@ This env var controls the [`discard-changes`](06-config.md#discard-changes) conf
 If set to 1, this env var will make Composer behave as if you passed the
 `--no-interaction` flag to every command. This can be set on build boxes/CI.
 
-### COMPOSER_DISABLE_XDEBUG_WARN
-
-If set to 1, this env disables the warning about having xdebug enabled.
-
 ### COMPOSER_ALLOW_SUPERUSER
 
 If set to 1, this env disables the warning about running commands as root/super user.