Remove PHP 8 from composer.json

Problem/Motivation

Right now, our composer.json allows PHP 8, since Open Social is not fully tested, therefore supported, we need to remove it from Open Social 11

Steps to reproduce

N/A

Proposed resolution

Remove php8 from composer.json

Remaining tasks

N/A

User interface changes

N/A

API changes

N/A

Data model changes

N/A