Update a Java book URL - #2990 (#3423)

* Update a Java book URL - #2990

Changes:
- The book 'Object-Oriented vs. Functional Programming' has a .csp link
- Also a sign-up is required to read the book since it's hosted at oreilly.com
- The contributing guide is against a hosting service and required sign-up.
- That is why this PR is created.

* remove ? link

Co-authored-by: Eric Hellman <eric@hellman.net>

free-programming-books.md

@@ -1492,7 +1492,6 @@ Kerridge (PDF) (email address *requested*, not required)
 * [Neural Network Development with Java](https://www.packtpub.com/packt/free-ebook/neural-networks-java) - Alan M. F. Souza and Fabio M. Soares (email address *requested*, not required)
 * [Object-Oriented Programming in JavaTM Textbook](http://computing.southern.edu/halterman/OOPJ/) - Rick Halterman (PDF per Chapter)
 * [Object Oriented Programming using Java](https://bookboon.com/en/object-oriented-programming-using-java-ebook) - Simon Kendal (PDF) , Bookboon. (email address *requested*, not required)
-* [Object-Oriented vs. Functional Programming](http://www.oreilly.com/programming/free/object-oriented-vs-functional-programming.csp) - Richard Warburton (email address *requested*, not required)
 * [OOP - Learn Object Oriented Thinking & Programming](http://pub.bruckner.cz/titles/oop) - Rudolf Pecinovsky (PDF)
 * [Open Data Structures (in Java)](http://opendatastructures.org/ods-java.pdf) - Pat Morin (PDF)
 * [Processing XML with Java (A Guide to SAX, DOM, JDOM, JAXP, and TrAX) (2002)](http://www.cafeconleche.org/books/xmljava/) - Elliotte Rusty Harold