Fix Gradle plugin documentation links

See gh-19961

Author: dreis2211

spring-boot-project/spring-boot-tools/spring-boot-gradle-plugin/src/main/asciidoc/getting-started.adoc

@@ -97,7 +97,7 @@ endif::[]
 Applied in isolation the plugin makes few changes to a project.
 Instead, the plugin detects when certain other plugins are applied and reacts accordingly.
 For example, when the `java` plugin is applied a task for building an executable jar is automatically configured.
-A typical Spring Boot project will apply the {groovy-plugin}[`groovy`], {java-plugin}java_plugin.html[`java`], or {kotlin-plugin}[`org.jetbrains.kotlin.jvm`] plugin and the {dependency-management-plugin}[`io.spring.dependency-management`] plugin as a minimum.
+A typical Spring Boot project will apply the {groovy-plugin}[`groovy`], {java-plugin}[`java`], or {kotlin-plugin}[`org.jetbrains.kotlin.jvm`] plugin and the {dependency-management-plugin}[`io.spring.dependency-management`] plugin as a minimum.
 For example: