Use consistent XML docbook namespace format

Reorder XML namespace imports for consistency with other docbook
files.

src/reference/docbook/testing.xml

@@ -1,12 +1,12 @@
 <?xml version="1.0" encoding="UTF-8"?>
-<chapter version="5.0"
-         xsi:schemaLocation="http://docbook.org/ns/docbook http://www.docbook.org/xml/5.0/xsd/docbook.xsd http://www.w3.org/1999/xlink http://www.docbook.org/xml/5.0/xsd/xlink.xsd"
-         xml:id="testing" xmlns="http://docbook.org/ns/docbook"
-         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
-         xmlns:xs="http://www.w3.org/2001/XMLSchema"
+<chapter xml:id="testing"
+	xmlns="http://docbook.org/ns/docbook" version="5.0"
     xmlns:xl="http://www.w3.org/1999/xlink"
     xmlns:xi="http://www.w3.org/2001/XInclude"
-         xmlns:ns="http://docbook.org/ns/docbook">
+    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+    xsi:schemaLocation="
+        http://docbook.org/ns/docbook http://www.docbook.org/xml/5.0/xsd/docbook.xsd
+        http://www.w3.org/1999/xlink http://www.docbook.org/xml/5.0/xsd/xlink.xsd">
   <title>Testing</title>
 
   <section xml:id="testing-introduction">