Add php 8.3 to the test matrix

[yalsicor]

Description

This adds PHP 8.3 to the testing matrix. This is in line with the current Laravel 10 supported PHP versions.

Type of change

• Bug fix (non-breaking change which fixes an issue)
• Refactor (refactoring a current feature, method, etc...)
• Code Coverage (adding/removing/updating/refactoring tests)
• New feature (non-breaking change which adds functionality)
• Remove feature (non-breaking change which removes functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)

[yalsicor]

Looks like the culprit is laravel/passport package.
Even on the latest stable release 12.3.0 it still requires league/oauth2-server: ^8.5.3, which in turn requires lcobucci/clock, which fixes the PHP version to either 8.1 or 8.2.
Upgrading that package to a later version which supports php8.3 drops php8.1 support.

So I think the best way of dealing with this is wait until we switch to Laravel 11, dropping php8.1 support anyway.