Upgrade to io.spring.asciidoctor:spring-asciidoctor-extensions-block-switch dependency version 0.6.1.

Pull dependency from Maven Central.

Author: jxblum

buildSrc/src/main/java/io/spring/gradle/convention/AsciidoctorConventionPlugin.java

@@ -67,7 +67,7 @@
 public class AsciidoctorConventionPlugin implements Plugin<Project> {
 
 	private static final String SPRING_ASCIIDOCTOR_BACKENDS_VERSION = "0.0.5";
-	private static final String SPRING_ASCIIDOCTOR_EXTENSIONS_BLOCK_SWITCH_VERSION = "0.4.2.RELEASE";
+	private static final String SPRING_ASCIIDOCTOR_EXTENSIONS_BLOCK_SWITCH_VERSION = "0.6.1";
 	private static final String SPRING_DOC_RESOURCES_VERSION = "0.2.5";
 
 	private static final String SPRING_ASCIIDOCTOR_BACKENDS_DEPENDENCY =