Update book title and URL in README

Author: Nicolai Parlog

README.md

@@ -1,6 +1,6 @@
 # ServiceMonitor
 
-An example application for my book [_The Java 9 Module System_](https://www.manning.com/books/the-java-9-module-system?a_aid=nipa&a_bid=869915cb).
+An example application for my book [_The Java Module System_](https://www.manning.com/books/the-java-module-system?a_aid=nipa&a_bid=869915cb).
 The _Service Monitor_ is an application that observes a hypothetical network of microservices by
 
 * contacting individual services