Update phpcodesniffer to stable version 2

Summary:
The stable version of phpcodesniffer 2 has been released. The composer dependency has been
updated to that version

Test Plan: run `arc lint` if you have changed files or `arc lint src/*.php`

Reviewers: dkd-ebert, #forgetit-dev, claus.due

Reviewed By: #forgetit-dev, claus.due

Differential Revision: https://phabricator.dkd.de/D531