PEP 825: merging metadata yields same result irrespective of order

This was essentially the goal, but I originally had trouble wording it
properly.

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

Author: mgorny

peps/pep-0825.rst

@@ -319,8 +319,8 @@ the variant metadata across multiple variant wheels of the same package
 version and the index-level metadata file is consistent. They MAY
 require that keys other than ``variants`` have exactly the same values,
 or they may carefully merge their values, provided that no conflicting
-information is introduced, and the resolution results within a subset of
-variants do not change.
+information is introduced, and the result is the same irrespective of
+the order in which the wheels are processed.
 
 This file SHOULD NOT be considered immutable and MAY be updated in a
 backward compatible way at any point (e.g. when adding a new variant).
@@ -997,6 +997,9 @@ Change History
 
   - Clarified that feature values in ``variants`` dictionary are sets,
     and that they ought to be sorted when serializing.
+  - Changed the rule for merging variant metadata to state that the
+    result must be the same irrespective of wheel order. This conveys
+    the goal of avoiding ambiguous results clearer.
 
 - 17-Feb-2026