bzr-win32symlinks lp permission changes

[Martin Pool]

Launchpad (Curtis) recently sent a notification that the
bzr-win32symlinks plugin is owned by an open team, ~bzr-windows.
Allowing an open team to have control rights is is a configuration
they're shortly going to disallow.  This team seems to exist mostly as
a list so I'm going to leave it open and then change bzr-win32symlinks
to be controlled by ~bzr.

If this breaks anything important to you let me know.

Martin