Add Javadoc since to AbstractApplicationContextRunner.prepare()

See gh-31454

spring-boot-project/spring-boot-test/src/main/java/org/springframework/boot/test/context/runner/AbstractApplicationContextRunner.java

@@ -349,6 +349,7 @@ public abstract class AbstractApplicationContextRunner<SELF extends AbstractAppl
 	 * consumed context.
 	 * @param consumer the consumer of the created {@link ApplicationContext}
 	 * @return this instance
+	 * @since 3.0.0
 	 */
 	@SuppressWarnings("unchecked")
 	public SELF prepare(ContextConsumer<? super A> consumer) {