Remove new upstream-supported environment variables from disallowed list

rabbitmq/content.md

@@ -37,12 +37,8 @@ For a list of environment variables supported by RabbitMQ itself, see the [Envir
 
 ```bash
 # Unavailable in 3.9 and up
-RABBITMQ_DEFAULT_PASS
 RABBITMQ_DEFAULT_PASS_FILE
-RABBITMQ_DEFAULT_USER
 RABBITMQ_DEFAULT_USER_FILE
-RABBITMQ_DEFAULT_VHOST
-RABBITMQ_ERLANG_COOKIE
 RABBITMQ_MANAGEMENT_SSL_CACERTFILE
 RABBITMQ_MANAGEMENT_SSL_CERTFILE
 RABBITMQ_MANAGEMENT_SSL_DEPTH