Fixup reference guide following dependencies move

Update reference guide to indicate that spring-boot-dependencies should
be imported when not using the parent POM.

spring-boot-docs/src/main/asciidoc/using-spring-boot.adoc

@@ -77,7 +77,7 @@ keep the benefit of the dependency management (but not the plugin management) us
 			<dependency>
 				<!-- Import dependency management from Spring Boot -->
 				<groupId>org.springframework.boot</groupId>
-				<artifactId>spring-boot-starter-parent</artifactId>
+				<artifactId>spring-boot-dependencies</artifactId>
 				<version>{spring-boot-version}</version>
 				<type>pom</type>
 		        <scope>import</scope>