Update base image for 8.19 docker default image to ubuntu 24.04

Author: breskeby

build-tools-internal/src/main/java/org/elasticsearch/gradle/internal/DockerBase.java

@@ -13,7 +13,7 @@
  * This class models the different Docker base images that are used to build Docker distributions of Elasticsearch.
  */
 public enum DockerBase {
-    DEFAULT("ubuntu:20.04", "", "apt-get", "dockerfiles/default/Dockerfile"),
+    DEFAULT("ubuntu:24.04", "", "apt-get", "dockerfiles/default/Dockerfile"),
 
     // "latest" here is intentional, since the image name specifies "8"
     UBI("docker.elastic.co/ubi8/ubi-minimal:latest", "-ubi8", "microdnf", "Dockerfile"),