Doc bug: Inaccurate text about replace operations

[quanah]

Doc/reference/ldap-modlist.rst has the following text:

   .. note::
      Replacing attribute values is always done with a
      :py:const:`ldap.MOD_DELETE`/:py:const:`ldap.MOD_ADD` pair instead of
      :py:const:`ldap.MOD_REPLACE` to work-around potential issues with
      attributes for which no EQUALITY matching rule are defined in the
      server's subschema.  This works correctly in most situations but
      rarely fails with some LDAP servers implementing (schema) checks on
      transient state entry during processing the modify operation.

This text seems to be incorrect, since it is doing an MOD_ADD or MOD_DELETE of a specific attribute value that requires matching rules to exist, and one usually uses a MOD_REPLACE operation to do the change to avoid the issue.