[DOC] onException blocks not shared when using a mix of Java/Spring DSLs

We hit an issue that onException blocks not shared when using a mix of Java/Spring DSLs. We were told that:
The OnException setting is just set on RouteBuilder.
As the Spring DSL and Java DSL do not share same RouteBuilder, the OnException setting cannot be shared yet even they are in the same camel context.
So we suggest you use either the spring DSL or the Java DSL, and do not use them mixed.

We have seen comments on forums where people (including Claus) explain that Spring and Java DSL can be freely mixed. As exception management is part of route design in general, this is very important to know. So we need the document updated.