repo: remove now-unused changectx() method (API)

repo: remove now-unused changectx() method (API)

repo.changectx(x) was just a synonym for repo[x], so any extensions
that fail due to this commit should switch over to that form.

Differential Revision: https://phab.mercurial-scm.org/D3037

--- a/mercurial/localrepo.py	Tue Apr 03 15:08:09 2018 -0700
+++ b/mercurial/localrepo.py	Tue Apr 03 13:19:35 2018 -0700
@@ -1073,9 +1073,6 @@
             f = f[1:]
         return filelog.filelog(self.svfs, f)
 
-    def changectx(self, changeid):
-        return self[changeid]
-
     def setparents(self, p1, p2=nullid):
         with self.dirstate.parentchange():
             copies = self.dirstate.setparents(p1, p2)

--- a/mercurial/repository.py	Tue Apr 03 15:08:09 2018 -0700
+++ b/mercurial/repository.py	Tue Apr 03 13:19:35 2018 -0700
@@ -493,12 +493,6 @@
     def file(f):
         """Obtain a filelog for a tracked path."""
 
-    def changectx(changeid):
-        """Obtains a changectx for a revision.
-
-        Identical to __getitem__.
-        """
-
     def setparents(p1, p2):
         """Set the parent nodes of the working directory."""