[6.x] Allow PHP 8.1

[Jubeki]

Github Actions Workflows indicate, that PHP 8.1 is supported. This PR adjusts the composer.json constraint accordingly.

nova-backup-tool/.github/workflows/run-tests.yml

Lines 8 to 18 in 06c75eb

	strategy:
	fail-fast: false
	matrix:
	php: [8.4, 8.3, 8.2, 8.1]
	laravel: [11.*, 10.*]
	dependency-version: [prefer-stable]
	exclude:
	- php: 8.1
	laravel: 11.*
	- php: 8.4
	laravel: 10.*

[freekmurze]

Thanks!