Update javadoc.

Author: jonathanaustin

taskmaster-cache-helper/src/main/java/com/github/bordertech/taskmaster/cache/servlet/CachingProviderListener.java

@@ -6,7 +6,7 @@
 import javax.servlet.ServletContextListener;
 
 /**
- * Cleanup any task master threads.
+ * Cleanup any cache resources when servlet context destroyed.
  */
 public class CachingProviderListener implements ServletContextListener {