[Log] "Where Logs are Stored" section is outdated

[lyrixx]

On : https://symfony.com/doc/current/logging.html#where-logs-are-stored

By default, log entries are written to the var/log/dev.log file when you’re in the dev environment. In the prod environment, logs are written to var/log/prod.log, but only during a request where an error or high-priority log entry was made (i.e. error() , critical(), alert() or emergency()).

This is not the case anymore. Now in production, log are sent to STDERR:

https://github.com/symfony/recipes/blob/master/symfony/monolog-bundle/3.7/config/packages/prod/monolog.yaml#L9-L13

& symfony/recipes#894