interfaces: drop the conditional import of the vendored `zope` packages

The real `zope` code was only used when enabled by a test, and the decorators
turned into no-ops at runtime.  Now that the test is disabled, unconditionally
use the no-op decorators and stop importing the code.  This module can go away
once the `mercurial.interfaces.repository` interfaces are converted to Protocol
classes, but the vendored code can be deleted in the meantime.

mercurial/interfaces/util.py

@@ -1,38 +1,30
 # util.py - Utilities for declaring interfaces.
 #
 # Copyright 2018 Gregory Szorc <[e-mail]>
 #
 # This software may be used and distributed according to the terms of the
 # GNU General Public License version 2 or any later version.
 
 # zope.interface imposes a run-time cost due to module import overhead and
 # bookkeeping for declaring interfaces. So, we use stubs for various
 # zope.interface primitives unless instructed otherwise.
 
 from __future__ import annotations
 
-from .. import encoding
-
-if encoding.environ.get(b'HGREALINTERFACES'):
-    from ..thirdparty.zope import interface as zi
-
-    Attribute = zi.Attribute
-    Interface = zi.Interface
-    implementer = zi.implementer
-else:
+if True:
 
     class Attribute:
         def __init__(self, __name__, __doc__=b''):
             pass
 
     class Interface:
         def __init__(
             self, name, bases=(), attrs=None, __doc__=None, __module__=None
         ):
             pass
 
     def implementer(*ifaces):
         def wrapper(cls):
             return cls
 
         return wrapper