[TASK] Remove post-autoload-dump section from composer.json

The included task in not subject to be executed upon each
`composer install`.

Resolves: #85537
Related: #83249
Releases: master, 8.7
Change-Id: I12240cbd7ea571b1872effd6942a3bd65bf37a89
Reviewed-on: https://review.typo3.org/57537


Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Susanne Moog <susanne.moog@typo3.org>
Tested-by: Susanne Moog <susanne.moog@typo3.org>
Reviewed-by: Mathias Brodala <mbrodala@pagemachine.de>
Tested-by: Mathias Brodala <mbrodala@pagemachine.de>