Actually drop copy.copy in Member

Remove the old and slow Member._copy implementation that was left over
by accident in 095f0ec.  Since it was defined later it overrode the new
implementation and rendered it moot.

discord/member.py

@@ -25,7 +25,6 @@ DEALINGS IN THE SOFTWARE.
 """
 
 import itertools
-import copy
 
 import discord.abc
 
@@ -225,11 +224,6 @@ class Member(discord.abc.Messageable, _BaseUser):
             u.avatar = user.get('avatar', u.avatar)
             u.discriminator = user.get('discriminator', u.discriminator)
 
-    def _copy(self):
-        c = copy.copy(self)
-        c._user = copy.copy(self._user)
-        return c
-
     @property
     def colour(self):
         """A property that returns a :class:`Colour` denoting the rendered colour