PHPDoc: Replace invalid "obj" with "object"
Summary:
Avoid "has invalid return type obj" errors when running static code analysis (PHPStan).
See https://docs.phpdoc.org/guide/references/phpdoc/types.html
Test Plan: Run PHPStan before and after applying this change (and its corresponding Arcanist change), get 15 errors less.
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/D25952