Remove uses of the 'future' py2->3 module

This is no longer needed, now that we are Py3.7+ only. One
layer of indirection removed, and one less dependency.

evennia/contrib/tutorial_world/objects.py

@@ -18,7 +18,6 @@ Weapon
 WeaponRack
 
 """
-from future.utils import listvalues
 
 import random
 
@@ -528,7 +527,7 @@ class CmdShiftRoot(Command):
         self.obj.db.root_pos = root_pos
 
         # Check victory condition
-        if listvalues(root_pos).count(0) == 0:  # no roots in middle position
+        if list(root_pos.values()).count(0) == 0:  # no roots in middle position
             # This will affect the cmd: lock of CmdPressButton
             self.obj.db.button_exposed = True
             self.caller.msg("Holding aside the root you think you notice something behind it ...")