Remove support for Resin Servlet container

This commit removes all references to the Resin Servlet container, as it
is not supported as of Spring Framework 6.0 because we require a
JakartaEE baseline.

Closes gh-33772

spring-web/src/main/java/org/springframework/web/util/WebAppRootListener.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2016 the original author or authors.
+ * Copyright 2002-2024 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -35,7 +35,7 @@ import jakarta.servlet.ServletContextListener;
  *
  * <p><b>WARNING</b>: Some containers, for example, Tomcat, do NOT keep system properties separate
  * per web app. You have to use unique "webAppRootKey" context-params per web app
- * then, to avoid clashes. Other containers like Resin do isolate each web app's
+ * then, to avoid clashes. Other containers do isolate each web app's
  * system properties: Here you can use the default key (i.e. no "webAppRootKey"
  * context-param at all) without worrying.
  *