Links to external packages in the documentation pointing to non existing Symfony code.

[marcinowski]

I've noticed it here, specifically for ProcessorInterface which in docs is annotated as Monolog\Processor\ProcessorInterface. The href points to https://github.com/symfony/symfony/blob/4.2/src/Monolog/Processor/ProcessorInterface.php which obviously doesn't exist, whereas I guess it should point to https://github.com/Seldaek/monolog/blob/master/src/Monolog/Processor/ProcessorInterface.php.