RFR JDK-8240921: Minor correction to HttpResponse.BodySubscribers example

[rahul . r . yadav]

Hello,

 Can I please have my fix reviewed for issue JDK-8240921 - Minor 
correction to HttpResponse.BodySubscribers example?

 The fix updates the incorrect example of the usage of the class 
java.net.http.HttpResponse.BodySubscribers.The patch also updates the 
test case for this scenario.

 Issue: https://bugs.openjdk.java.net/browse/JDK-8240921

 Webrev: 
http://cr.openjdk.java.net/~pconcannon/rayayada/8240921/webrevs/webrev.00/

- Rahul