Update documentation example to configure Reactive Transactional Support

[rajadilipkolli]

The example provided here is outdated and it should be updated. If someone can point to the github location I can raise a PR as well.

Example should be as below

@Configuration
public class Configuration extends AbstractReactiveMongoConfiguration {

    @Value("${spring.data.mongodb.database}")
    private String databaseName;

    @Bean
    ReactiveMongoTransactionManager transactionManager(ReactiveMongoDatabaseFactory factory) {
        return new ReactiveMongoTransactionManager(factory);
    }

    @Override
    protected String getDatabaseName() {
        return this.databaseName;
    }
}

[christophstrobl]

good catch - thanks for reporting!