Update lib/tasks.rb

My setup wouldn't work until I removed this line, because for
some reason, it sets staging_domain to an empty string no matter
what it's set to in config.rb. I don't know whether I was doing
something wrong or what, but removing line 71 from lib/tasks.rb worked
for me.

This isn't exactly a pull request I just figured it'd be an easier way
of showing you where I had a problem.