Clarify that negative concurrency values in CiCT can only be done through a parameter (neo4j#1128)

Author: JPryce-Aklundh

modules/ROOT/pages/subqueries/subqueries-in-transactions.adoc

@@ -601,7 +601,7 @@ This allows `CALL` subqueries to utilize multiple CPU cores simultaneously, whic
 [NOTE]
 The concurrency value is optional.
 If not specified, a default value based on the amount of available CPU cores will be chosen.
-If a negative number is specified, the concurrency will be the number of available CPU cores reduced by the absolute value of that number.
+If a negative number is specified (which can only be done through a parameter), the concurrency will be the number of available CPU cores reduced by the absolute value of that number.
 
 .Load a CSV file in concurrent transactions
 ====