Upgrade decisionserver63-basic-s2i in spring-boot-camel-drools readme

Spring-boot-camel-drools doesn't work with Openshift 3.7, if we go through the readme as there is mentioned decisionserver63-basic-s2i which is dropped in xpaas-templates for Openshift 3.7. So we should probably update the readme with decisionserver64-basic-s2i.