Mute old ES reindex tests (#80193)

Failing on ci see https://github.com/elastic/elasticsearch/issues/79898

modules/reindex/build.gradle

@@ -156,6 +156,12 @@ if (Os.isFamily(Os.FAMILY_WINDOWS)) {
   }
 }
 
+tasks.named("javaRestTest").configure {
+  //  DISABLE
+  //  RENE: We disable those tests for now due to failing on ci
+  //  See https://github.com/elastic/elasticsearch/issues/79898
+  enabled = false
+}
 tasks.named("yamlRestTestV7CompatTransform").configure { task ->
     task.skipTest("reindex/20_validation/reindex without source gives useful error message", "exception with a type. Not much benefit adding _doc there.")
     task.skipTest("update_by_query/20_validation/update_by_query without source gives useful error message", "exception with a type. Not much benefit adding _doc there.")