Fix checkstyle violation

Author: snicoll

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/web/ServerProperties.java

@@ -473,7 +473,7 @@ public static class Tomcat {
 		/**
 		 * Whether to reject requests with illegal header names or values.
 		 */
-		@Deprecated
+		@Deprecated(since = "2.7.12", forRemoval = true)
 		private boolean rejectIllegalHeader = true;
 
 		/**