Fix regression in DiffusionDiffQueryConduitAPIMethod

Summary:
Fix the following error you may encounter in production:

Too few arguments to function DiffusionDiffQueryConduitAPIMethod::getDefaultParser(), 0 passed in /var/www/phorge/src/applications/diffusion/conduit/DiffusionDiffQueryConduitAPIMethod.php on line 156 and exactly 1 expected

It was caused by the lack of a new mandatory parameter in a method.

Closes T15649

Test Plan: Check with your big eyes that a ConduitAPIRequest is passed to getDefaultParser().

Reviewers: avivey, O1 Blessed Committers, speck

Reviewed By: O1 Blessed Committers, speck

Subscribers: speck, tobiaswiese, Matthew, Cigaryno

Maniphest Tasks: T15649

Differential Revision: https://we.phorge.it/D25444