Addressing some PHP 8 incompatibilities - Remarkup

Summary:
Updating compatibility for PHP 8.2 for remarkup-related functionality.

This also resolves an issue introduced by https://secure.phabricator.com/D21860. Of all the flags when opening the zip the one I chose was not introduced in 5.2 but in 7.4

Test Plan: I rendered comments using figlet, cowsay, images, object references.

Reviewers: Blessed Reviewers, epriestley

Reviewed By: Blessed Reviewers, epriestley

Subscribers: Korvin, epriestley

Differential Revision: https://secure.phabricator.com/D21866