update document

xxl-job-core/src/main/java/com/xxl/job/core/executor/impl/XxlJobSpringExecutor.java

                     String name = serviceBean.getClass().getAnnotation(JobHandler.class).value();
                     IJobHandler handler = (IJobHandler) serviceBean;
                     if (loadJobHandler(name) != null) {
-                        throw new RuntimeException("xxl-job jobhandler naming conflicts.error name:"+name);
+                        throw new RuntimeException("xxl-job jobhandler["+ name +"] naming conflicts.");
                     }
                     registJobHandler(name, handler);
                 }