Drop obfs2 from bridge deployment instructions

These are the pages I'm referring to.

https://www.torproject.org/projects/obfsproxy-instructions.html.en https://www.torproject.org/projects/obfsproxy-debian-instructions.html.en

In order to discourage obfs2 deployment and use, the line

ServerTransportPlugin obfs2,obfs3 exec /usr/local/bin/obfsproxy managed

on both these pages could be replaced with

ServerTransportPlugin obfs3 exec /usr/local/bin/obfsproxy managed