Update scalability.adoc

Move commentary on xml configuration just below the configuration
it's explaining, instead of having it in the middle of the Java
configuration example.

Issue #4338

Author: kajsa

spring-batch-docs/src/main/asciidoc/scalability.adoc

@@ -302,6 +302,11 @@ configuration:
 </step>
 ----
 
+[role="xmlContent"]
+Similar to the multi-threaded step's `throttle-limit` attribute, the `grid-size`
+attribute prevents the task executor from being saturated with requests from a single
+step.
+
 [role="javaContent"]
 The following example shows the `PartitionStep` configuration when using Java
 configuration:
@@ -320,11 +325,6 @@ public Step step1Manager() {
 }
 ----
 
-[role="xmlContent"]
-Similar to the multi-threaded step's `throttle-limit` attribute, the `grid-size`
-attribute prevents the task executor from being saturated with requests from a single
-step.
-
 [role="javaContent"]
 Similar to the multi-threaded step's `throttleLimit` method, the `gridSize`
 method prevents the task executor from being saturated with requests from a single