DATAJDBC-509 - Fix findByFirstnameLike @Query example in README.

Original pull request: #198.

README.adoc

@@ -36,7 +36,7 @@ public interface PersonRepository extends CrudRepository<Person, Long> {
   @Query("SELECT * FROM person WHERE lastname = :lastname")
   List<Person> findByLastname(String lastname);
 
-  @Query("SELECT * FROM person WHERE firstname LIKE :lastname")
+  @Query("SELECT * FROM person WHERE firstname LIKE :firstname")
   List<Person> findByFirstnameLike(String firstname);
 }