Remove functionally empty irc directory.

The webkitpy/common/net/irc/ is functionally empty.
There is just a single __init__.py file present, all other
code was removed before. So now remove the whole directory.

BUG=none

Review URL: https://codereview.chromium.org/627333003

git-svn-id: svn://svn.chromium.org/blink/trunk@183402 bbb929c8-8fbe-4397-9dbb-9b2b20218538