Upgrade to Dokka 2.1.0-Beta

We need to upgrade for better compatibility with Java 25.

See gh-47413

Author: wilkinsona

buildSrc/src/main/java/org/springframework/boot/build/KotlinConventions.java

@@ -76,6 +76,7 @@ private void configure(KotlinCompile compile) {
 
 	private void configureDokkatoo(Project project) {
 		DokkatooExtension dokkatoo = project.getExtensions().getByType(DokkatooExtension.class);
+		dokkatoo.getVersions().getJetbrainsDokka().set("2.1.0-Beta");
 		dokkatoo.getDokkatooSourceSets().configureEach((sourceSet) -> {
 			if (SourceSet.MAIN_SOURCE_SET_NAME.equals(sourceSet.getName())) {
 				sourceSet.getSourceRoots().setFrom(project.file("src/main/kotlin"));