[CI] Updates ES_YAML_TESTS_BRANCH

Author: picandocodigo

.buildkite/pipeline.yml

@@ -63,7 +63,7 @@ steps:
     env:
       RUBY_VERSION: "3.3"
       STACK_VERSION: 8.17.0-SNAPSHOT
-      ES_YAML_TESTS_BRANCH: 8.x
+      ES_YAML_TESTS_BRANCH: 8.17
       TRANSPORT_VERSION: "8.3"
       RUBY_SOURCE: "ruby"
       TEST_SUITE: "platinum"