[TASK] Update rector/rector

    composer remove --dev rector/rector
    composer require --dev rector/rector:~0.6

The update of rector brings important bugfixes and
enables the installation of the latest version of
phpstan/phpstan.

Releases: master
Resolves: #89918
Change-Id: I406aa56b19e88db23260033023e2c785425aef5e
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/62599


Tested-by: TYPO3com <noreply@typo3.com>
Tested-by: Andreas Fernandez <a.fernandez@scripting-base.de>
Tested-by: Anja Leichsenring <aleichsenring@ab-softlab.de>
Reviewed-by: Andreas Fernandez <a.fernandez@scripting-base.de>
Reviewed-by: Anja Leichsenring <aleichsenring@ab-softlab.de>