R1:b9fb8d789151

Replace invalid PHPDoc @return type boolean with bool

Summary: `@return boolean` is not a valid type thus use `@return bool`.

Test Plan: None.

Reviewers: O1 Blessed Committers, valerio.bozzolan

Reviewed By: O1 Blessed Committers, valerio.bozzolan

Subscribers: tobiaswiese, valerio.bozzolan, Matthew, Cigaryno

Differential Revision: https://we.phorge.it/D25795