Fix Servlet exploits leveloffset

Fixes gh-2567

docs/manual/src/docs/asciidoc/_includes/servlet/exploits/index.adoc

@@ -1,7 +1,7 @@
 = Protection Against Exploits
 
-include::csrf.adoc[]
+include::csrf.adoc[leveloffset=+1]
 
-include::headers.adoc[]
+include::headers.adoc[leveloffset=+1]
 
-include::channel.adoc[]
+include::channel.adoc[leveloffset=+1]