Change the scope of stepVariable in allReduce. (#1401)

As of `2025.10.0`

Author: inmost-light

modules/ROOT/pages/functions/predicate.adoc

@@ -120,7 +120,7 @@ It is initialized with the value of `initial`.
 | `reductionFunction` | `ANY` | An expression whose return value becomes the next value of the `accumulator`.
 The return type must match the return type of `initial`.
 | `predicate` | `BOOLEAN` | A predicate that is evaluated for each iteration.
-It has access to the variable `accumulator`, but not `stepVariable`. 
+It has access to both the `accumulator` and `stepVariable` variables.
 | *Returns* 3+| `BOOLEAN`
 |===