dbus: don't do <deny send_interface="..." /> in dbus service file

dbus: don't do <deny send_interface="..." /> in dbus service file

It does more than intended; apart from denying messages to that particular
interface it also denies all messages non-qualified with an
interface globally.
This blocks messages completely unrelated to wpa_supplicant, such as
NetworkManager communication with the VPN plugins.

From the dbus-daemon manual:

  Be careful with send_interface/receive_interface, because the
  interface field in messages is optional. In particular, do NOT
  specify <deny send_interface="org.foo.Bar"/>! This will cause
  no-interface messages to be blocked for all services, which is
  almost certainly not what you intended. Always use rules of the form:
  <deny send_interface="org.foo.Bar" send_destination="org.foo.Service"/>

We can just safely remove those rules, since we're sufficiently protected
by the send_destination matches and method calls are disallowed by default
anyway.

https://bugzilla.gnome.org/show_bug.cgi?id=763880