why remove support for laravel 9?

@TavoNiievez wrote that come work is required to support Laravel 9 at #40 (comment)

@TavoNiievez @Naktibalda Any plans to support Laravel 9 soon? I would like to update but this is blocking me

Hi @applyACS ,
and by extension @liamh101 , @nablejohn , @dmoreno and @themaric

The laravel 8.0 restriction is included in the require-dev section of the composer.json file. This means that when you try to composer install composer update this module composer will ignore any value that is written in this section.

This is only useful if you are a maintainer or contributor of the module and want to make any changes to it, for which it might help to have Laravel dependencies installed and get autocompletion in your IDE.

None of the dependencies in the require section conflict with higher versions of Laravel so it is not possible that the value you are trying to modify in this PR could have meant a blocker for your upgrade as you stated in your comment.

I asked @Naktibalda not to update this value yet, because updating it implies:

1. That a maintainer thoroughly reviewed the source code and verified that all of the Laravel version enhancements in question that are intended to be added were uniformly integrated throughout the source code.

2. That a maintainer created a branch in the laravel-module-tests project with a Laravel installation that uses the version intended to be added and verified that all tests work as well as that the application source code integrates all enhancements from the latest Laravel version.

Without this, updating that value makes no sense at all.

That is why I am closing this PR.