Fix reST formatting for Java code block

Author: till-varoquaux

peps/pep-0835.rst

@@ -108,6 +108,7 @@ ecosystems, notably Java. In Java (formalized in `JSR 308 <https://jcp.org/en/js
 and other JVM languages, the ``@`` symbol is standard for type annotations:
 
 .. code-block:: java
+
     public class Person {
         @Column(length = 32)
         private String name;