Clarify that "list of compatible values" must also be ordered

Thanks to Kroppeb for pointing this out in
https://discuss.python.org/t/pep-825-wheel-variants-package-format-split-from-pep-817/106196/4

Signed-off-by: Michał Górny <mgorny@quansight.com>

Author: mgorny

peps/pep-0825.rst

@@ -372,8 +372,8 @@ properties.
 For the purpose of ordering, variant properties are grouped into
 features, and features into namespaces. For every namespace, the tool
 MUST obtain an ordered list of compatible features, and for every
-feature, a list of compatible values. The method of obtaining these
-lists will be defined in a subsequent PEP.
+feature, an ordered list of compatible values. The method of obtaining
+these lists will be defined in a subsequent PEP.
 
 The ordering MUST be performed equivalent to the following algorithm: