Fixed license linter

Summary: `ArcanistWorkingCopyIdentity.getConfig()` has been replaced by more specific config retireval methods. This changes the using the appropriate new method.

Test Plan: Run the linter.

Reviewers: mbishop

Reviewed By: mbishop

Subscribers: jstarke, mbishop

Differential Revision: https://devportal.imobile3.com/D9914