From https://www.drupal.org/docs/develop/using-composer/add-a-composerjson-fi... →
If your project does have a composer.json file, having a drupal/core version requirement is also not required for Drupal 9 compatibility. It is better not to provide a drupal/core version requirement in composer.json because Drupal's composer facade will generate the appropriate metadata based on the info.yml file.
And speaking as a site maintainer, modules that include core as a dependency can be a little troublesome if you have to do something weird while updating dependencies.
Delete the requirement.
Delete the requirement.
Fixed
2.0
Code
I'll leave this open for a few days in case anyone wants to comment on it.
Automatically closed - issue fixed for 2 weeks with no activity.