R1:10cf2bb4e2f3

Mark PhabricatorRepositorySvnCommitChangeParserWorker as final

Test Plan:
$ git grep PhabricatorRepositorySvnCommitChangeParserWorker

Reviewers: epriestley

Reviewed By: epriestley

CC: aran, Korvin

Differential Revision: https://secure.phabricator.com/D3897