DOC: Fixed invalid classdoc reference

Author: mattgebert

doc/validation.rst

@@ -183,7 +183,7 @@ inline comments:
         def __init__(self):  # numpydoc ignore=GL08
             pass
 
-Note, if the :ref:`class <_classdoc>` docstring properly documents the
+Note, if the :ref:`class <classdoc>` docstring properly documents the
 constructor, the ``GL08`` will be ignored by default.
 
 This is supported by the :ref:`CLI <validation_via_cli>`,