Do not modify AliasChecks list from Jetty WebAppContext

Closes gh-29555
Signed-off-by: Lachlan Roberts <[email protected]>

Author: lachlan-roberts

spring-boot-project/spring-boot/src/main/java/org/springframework/boot/web/embedded/jetty/JettyServletWebServerFactory.java

@@ -218,7 +218,7 @@ private void customizeSsl(Server server, InetSocketAddress address) {
 	 */
 	protected final void configureWebAppContext(WebAppContext context, ServletContextInitializer... initializers) {
 		Assert.notNull(context, "Context must not be null");
-		context.getAliasChecks().clear();
+		context.clearAliasChecks();
 		context.setTempDirectory(getTempDirectory());
 		if (this.resourceLoader != null) {
 			context.setClassLoader(this.resourceLoader.getClassLoader());