Fix DotEnv dependency
Summary:
Recent DotEnv versions are built through DotEnv::createImmutable.
To prevent further changes (if any) to break the installation,
pin the current PHP 8.2 compatible version to composer.
Test Plan: Browse wiki, the environment variables are correctly read
Reviewers: dereckson
Reviewed By: dereckson
Differential Revision: https://devcentral.nasqueron.org/D3050