Enforce opening brace is on same line than method declaration

Summary:
Nasqueron uses K&R style, Laravel not, this change standardizes
the Laravel-generated code.

This is a follow-up for 85fc0f62b8e1 (same change for classes).

Test Plan: phpcs with Generic.Functions.OpeningFunctionBraceKernighanRitchie sniff

Reviewers: dereckson

Reviewed By: dereckson

Differential Revision: https://devcentral.nasqueron.org/D1547