Auto trigger DRA for all 8.x branches (elastic#39386)

This commit adds 7.17 to the whitelist of branches that may trigger
Buildkite DRA builds.

Relates: elastic/ingest-dev#3095

catalog-info.yaml

@@ -1040,9 +1040,7 @@ spec:
     spec:
       repository: elastic/beats
       pipeline_file: ".buildkite/packaging.pipeline.yml"
-      branch_configuration: "main 8.*"
-      # TODO enable after packaging backports for release branches
-      # branch_configuration: "main 8.* 7.17"
+      branch_configuration: "main 8.* 7.17"
       cancel_intermediate_builds: false
       skip_intermediate_builds: false
       maximum_timeout_in_minutes: 90