docs: usermanual: reorder gb/ns2 chapter to keep all ns2 part together

Change-Id: I3bc1c4de090a073cf1b1a6fe852f17857754beaf
diff --git a/doc/manuals/osmogbproxy-usermanual.adoc b/doc/manuals/osmogbproxy-usermanual.adoc
index 4de5106..c371cf7 100644
--- a/doc/manuals/osmogbproxy-usermanual.adoc
+++ b/doc/manuals/osmogbproxy-usermanual.adoc
@@ -21,13 +21,14 @@
 
 include::{srcdir}/chapters/gbproxy-configuration.adoc[]
 
+include::{srcdir}/chapters/gbproxy-sgsnpool.adoc[]
+
+include::./common/chapters/gb-ns2.adoc[]
+
 include::./common/chapters/gb-ns2-configuration.adoc[]
 
 include::./common/chapters/gb-ns2-configuration-timer.adoc[]
 
-include::{srcdir}/chapters/gbproxy-sgsnpool.adoc[]
-
-include::./common/chapters/gb-ns2.adoc[]
 
 include::./common/chapters/control_if.adoc[]