FOP-3327 Fix leader code snippet

content/fop/trunk/extensions.mdtext

diff --git a/content/fop/trunk/extensions.mdtext b/content/fop/trunk/extensions.mdtext
index 51a2582..0724bbd 100644
--- a/content/fop/trunk/extensions.mdtext
+++ b/content/fop/trunk/extensions.mdtext
@@ -392,7 +392,7 @@
 
 Applies to: fo:leader (with `leader-pattern="rule"`)
 
-:::xml
+    :::xml
     <fo:leader leader-pattern="rule"
                fox:rule-style="square"
                rule-thickness="2pt"