change when false into commented code

lib/pure/collections/sets.nim

@@ -578,18 +578,16 @@ proc hash*[A](s: HashSet[A]): Hash =
   # This handles tombstones (iterating over all `s.data` would be wrong).
   # Iterating over items(s) requires a commutative hash combiner like `xor`
   # to avoid depending on order (which could differ for 2 HashSet's with different
-  # `data.len` but same elements, after insertions and deletions). But `xor`
-  # has bad mixing properties (eg, would give 0 if HashSet contains
+  # `data.len` but same elements, after insertions and deletions), eg:
+  #   for h in s:
+  #     result = result xor hash(h)
+  # But `xor` has bad mixing properties (eg, would give 0 if HashSet contains
   # a, b such that hash(a) == hash(b) and a != b). `sort` should have low
   # overhead compared to the surrounding code.
-  when true:
-    var s2: seq[Hash]
-    for h in s: s2.add hash(h)
-    s2.sort
-    for h in s2: result = result !& hash(h)
-  else:
-    for h in s:
-      result = result xor hash(h)
+  var s2: seq[Hash]
+  for h in s: s2.add hash(h)
+  s2.sort
+  for h in s2: result = result !& hash(h)
   result = !$result
 
 proc `$`*[A](s: HashSet[A]): string =