Use a recent version number in sample POM code

OWASP#41

Author: mikesamuel

docs/maven.md

@@ -9,7 +9,7 @@ Including among your POMs `<dependencies>` this snippet of XML
 <dependency>
  <groupId>com.googlecode.owasp-java-html-sanitizer</groupId>
  <artifactId>owasp-java-html-sanitizer</artifactId>
- <version>[r136,)</version>
+ <version>[r239,)</version>
 </dependency>
 ```