Fix minor docbug

Author: IoannisPanagiotas

doc/modules/ROOT/pages/management-ops/graph-update/to-undirected.adoc

@@ -43,7 +43,7 @@ YIELD
 | Name                   | Type                  | Default | Optional | Description
 | relationshipType       | String                | n/a     | no       | The relationship type to make undirected.
 | mutateRelationshipType | String                | n/a     | no       | The relationship type to be added to the graph.
-| aggregation            | Map or String         | n/a     | no       | Handling of parallel relationships. Allowed values are `NONE`, `MIN`, `MAX`, `SUM`, `SINGLE`, `COUNT`. Using map allows specifying aggregations per relationship property. By default we will use the existing aggregation used during the initial projection.
+| aggregation            | Map or String         | `NONE`    | yes       | Handling of parallel relationships. Allowed values are `NONE`, `MIN`, `MAX`, `SUM`, `SINGLE`, `COUNT`. Using map allows specifying aggregations per relationship property. By default we will use the existing aggregation used during the initial projection.
 include::partial$/algorithms/common-configuration/common-configuration-jobid-concurrency-entries.adoc[]
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