Remove libphutil mentions from Phorge codebase
Summary:
Remove references to libphutil in documentation exposed to users.
(For the records: libphutil's `launch_daemon.php` was deleted in rPHU720c8116 and not added in rARC9b74cb4e, thus deleted that reference completely.)
Refs T15015
Test Plan: Read and grep.
Reviewers: O1 Blessed Committers, mainframe98
Reviewed By: O1 Blessed Committers, mainframe98
Subscribers: tobiaswiese, valerio.bozzolan, Matthew, Cigaryno
Maniphest Tasks: T15015
Differential Revision: https://we.phorge.it/D26255