Revert back to S3 repository for ML snapshot artifacts (elastic#92381)

We have been having issues with reliability of downloads of artifacts
from our GCS-backed artifact repository. The root cause has been
identified and reported to GCP and a production fix is incoming. The
current ETA is January so let's just revert for now to reduce some of
the CI failure noise.

This change only affects development builds. Both snapshot and staging
builds will continue to use DRA artifacts downloaded by CI.

x-pack/plugin/ml/build.gradle

@@ -1,6 +1,3 @@
-import org.elasticsearch.gradle.VersionProperties
-import org.elasticsearch.gradle.internal.dra.DraResolvePlugin
-
 apply plugin: 'elasticsearch.internal-es-plugin'
 apply plugin: 'elasticsearch.internal-cluster-test'
 apply plugin: 'elasticsearch.internal-test-artifact'
@@ -14,42 +11,27 @@ esplugin {
   extendedPlugins = ['x-pack-autoscaling', 'lang-painless']
 }
 
-def localRepo = providers.systemProperty('build.ml_cpp.repo').orNull
 if (useDra == false) {
   repositories {
     exclusiveContent {
-      filter {
-        includeGroup 'org.elasticsearch.ml'
-      }
       forRepository {
         ivy {
           name "ml-cpp"
+          url providers.systemProperty('build.ml_cpp.repo').orElse('https://prelert-artifacts.s3.amazonaws.com').get()
           metadataSources {
             // no repository metadata, look directly for the artifact
             artifact()
           }
-          if (localRepo) {
-            url localRepo
-            patternLayout {
-              artifact "maven/[orgPath]/[module]/[revision]/[module]-[revision](-[classifier]).[ext]"
-            }
-          } else {
-            url "https://artifacts-snapshot.elastic.co/"
-            patternLayout {
-              if (VersionProperties.isElasticsearchSnapshot()) {
-                artifact '/ml-cpp/[revision]/downloads/ml-cpp/[module]-[revision]-[classifier].[ext]'
-              } else {
-                // When building locally we always use snapshot artifacts even if passing `-Dbuild.snapshot=false`.
-                // Release builds are always done with a local repo.
-                artifact '/ml-cpp/[revision]-SNAPSHOT/downloads/ml-cpp/[module]-[revision]-SNAPSHOT-[classifier].[ext]'
-              }
-            }
+          patternLayout {
+            artifact "maven/org/elasticsearch/ml/ml-cpp/[revision]/[module]-[revision](-[classifier]).[ext]"
           }
         }
       }
+      filter {
+        includeGroup 'org.elasticsearch.ml'
+      }
     }
   }
-
 }
 
 configurations {
@@ -130,4 +112,4 @@ tasks.named("dependencyLicenses").configure {
   mapping from: /lucene-.*/, to: 'lucene'
 }
 
-addQaCheckDependencies(project)
+addQaCheckDependencies(project)