user doc: Added a prereq that you need to know Camel Simple Exp, or have a filter expression
@@ -13,6 +13,8 @@ define the exact filter that you need, then add an advanced filter step.
.Prerequisites
* The flow contains all connections that it needs to.
* You are creating or editing a flow.
+* You are familiar with the Camel Simple Expression language, or
+you have been provided with a filter expression.
.Procedure
