Fix checkstyle

Author: snicoll

core/spring-boot-test/src/main/java/org/springframework/boot/test/system/OutputCaptureRule.java

@@ -52,7 +52,7 @@
  * @since 2.2.0
  * @deprecated since 4.0.0 in favor of JUnit 5 and {@link OutputCaptureExtension}
  */
-@Deprecated
+@Deprecated(since = "4.0.0")
 public class OutputCaptureRule implements TestRule, CapturedOutput {
 
 	private final OutputCapture delegate = new OutputCapture();