Don't set YYINITDEPTH

Summary: I have no idea why this was added originally, but it doesn't seem to be necessary anymore.

Test Plan: Ran arc unit --everything in rARC, rPHU and rP.

Reviewers: epriestley, Blessed Reviewers

Reviewed By: epriestley, Blessed Reviewers

Subscribers: Korvin, epriestley

Differential Revision: https://secure.phabricator.com/D14529