Remove dead "Converting a jar to a war" guide link

See gh-42691

spring-boot-project/spring-boot-docs/src/docs/asciidoc/howto/traditional-deployment.adoc

@@ -72,7 +72,6 @@ This means that, in addition to being deployable to a servlet container, you can
 === Convert an Existing Application to Spring Boot
 To convert an existing non-web Spring application to a Spring Boot application, replace the code that creates your `ApplicationContext` and replace it with calls to `SpringApplication` or `SpringApplicationBuilder`.
 Spring MVC web applications are generally amenable to first creating a deployable war application and then migrating it later to an executable war or jar.
-See the https://spring.io/guides/gs/convert-jar-to-war/[Getting Started Guide on Converting a jar to a war].
 
 To create a deployable war by extending `SpringBootServletInitializer` (for example, in a class called `Application`) and adding the Spring Boot `@SpringBootApplication` annotation, use code similar to that shown in the following example: