Fix implicitly nullable parameter declarations for PHP 8.4
Summary:
Implicitly nullable parameter declarations are deprecated in PHP 8.4:
https://php.watch/versions/8.4/implicitly-marking-parameter-type-nullable-deprecated
The proposed syntax was introduced in PHP 7.1.
This patch is a followup on top of D25814.
Refs T15935
Test Plan:
* Try to view a task in the browser
* Try to run `./bin/auth recover` on the CLI
* Try to browse projects in the browser
* Try to create a new project without a name in the browser
Reviewers: O1 Blessed Committers, chris
Reviewed By: O1 Blessed Committers, chris
Subscribers: tobiaswiese, valerio.bozzolan, Matthew, Cigaryno
Maniphest Tasks: T15935
Differential Revision: https://we.phorge.it/D25816