vfs: drop the 'mustaudit' API

There are no remaining users of 'mustaudit' so we can safely drop the API.
External user are unlikely from a quick research so no deprecation is added.

mercurial/vfs.py

@@ -290,21 +290,13 @@ class vfs(abstractvfs):
         if realpath:
             base = os.path.realpath(base)
         self.base = base
-        self.mustaudit = audit
-        self.createmode = None
-        self._trustnlink = None
-
-    @property
-    def mustaudit(self):
-        return self._audit
-
-    @mustaudit.setter
-    def mustaudit(self, onoff):
-        self._audit = onoff
-        if onoff:
+        self._audit = audit
+        if audit:
             self.audit = pathutil.pathauditor(self.base)
         else:
             self.audit = util.always
+        self.createmode = None
+        self._trustnlink = None
 
     @util.propertycache
     def _cansymlink(self):
@@ -435,14 +427,6 @@ class auditvfs(object):
     def __init__(self, vfs):
         self.vfs = vfs
 
-    @property
-    def mustaudit(self):
-        return self.vfs.mustaudit
-
-    @mustaudit.setter
-    def mustaudit(self, onoff):
-        self.vfs.mustaudit = onoff
-
     @property
     def options(self):
         return self.vfs.options