Remove "core: 8.x" from the .info.yml file

Hello Maintainers,
I have provided a patch to fix this issue.
To get more information visit https://www.drupal.org/node/3070687 →
Please review it.

Thanks!

This make sense, this module also needs a D10 version, so there will a 9 and 10 version released with the proper info metadata. I will also be dropping 8 from supported development. You can always use a previous version.

 package: Mail
-core: 8.x
 core_version_requirement: ^8 || ^9

Modules, themes. and profiles are allowed to use the following lines in their .info.yml file.

core: 8.x
core_version_requirement: ^8 || ^9

That is described in New 'core_version_requirement' key in info.yml files for modules, themes and profiles → allows Composer semantic version constraints including specifying multiple major versions of core, which states:

For example a module that is compatible with Drupal 8 and Drupal 9 can have a info.yml file like this

name: My Module
type: module
core: 8.x
core_version_requirement: ^8 || ^9

There is no change that must be done in that .info.yml file.