I made a composer diagnose
and got the following error message:
WARNING symfony/monolog-bundle is required both in require and require-dev, this can lead to unexpected behavior require.symfony/serializer-pack : unbound version constraints () should be avoided require.symfony/webpack-encore-pack : unbound version constraints () should be avoided
How can I use monolog-bundle only in require-dev?
Rerun composer require symfony/monolog-bundle --dev
that should fix your issue.
Another way would be to edit your composer.json and remove the package out of the section require
but keeping it in the section require-dev