Dropping PhpSpec development dependency

[J-Brk]

Problem

The development dependencies require "phpspec/phpspec": "~5.1.1 || ^6.0".
This version is not compatible with newer PHP versions; PHP 7.4 and above.

PhpSpec seems to be barely used and can be found in two places:

• spec/Artesaos/SEOTools/OpenGraphSpec.php
• spec/Artesaos/SEOTools/SEOMetaSpec.php.

The last commit regarding those 2 files where in 2016.

Proposed solution

Dropping PhpSpec or alternatively upgrading it to a newer version.

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Package Version v0.22.0 / PHP version 8.1.2