Remove a check for a non-existing array offset
Summary:
`$style` is never read again in this function, and as the line `'style' => implode(' ', $default_style)` got removed in rPeb73c50e so it can never exist as an array offset.
`DiffusionRepositoryProfilePictureController` is a copy of `PhabricatorPeopleProfilePictureController` so also remove there.
Test Plan: Read the code.
Reviewers: O1 Blessed Committers, mainframe98
Reviewed By: O1 Blessed Committers, mainframe98
Subscribers: tobiaswiese, valerio.bozzolan, Matthew, Cigaryno
Differential Revision: https://we.phorge.it/D26506