MNT: simplify deprecation of numdecs attribute

Co-authored-by: Elliott Sales de Andrade <[email protected]>

Author: rcomer

lib/matplotlib/ticker.py

@@ -2269,15 +2269,7 @@ def set_params(self, base=None, subs=None, numdecs=None, numticks=None):
         if numticks is not None:
             self.numticks = numticks
 
-    @_api.deprecated("3.8", addendum="This attribute has no effect.")
-    @property
-    def numdecs(self):
-        return self._numdecs
-
-    @_api.deprecated("3.8", addendum="This attribute has no effect.")
-    @numdecs.setter
-    def numdecs(self, numdecs):
-        self._numdecs = numdecs
+    numdecs = _api.deprecate_privatize_attribute("3.8", addendum="This attribute has no effect.")
 
     def _set_subs(self, subs):
         """