Verify and remove unsued index on ci_builds_table

Background

In order to complete #230438 (closed) a new index index_partial_ci_builds_on_user_id_name_type_parser_features to ci_builds was added (by !37581 (merged)), most likely it will be preferred over old index_secure_ci_builds_on_user_id_created_at_parser_features by the planner. We should verify (as it is described here) if that is the case, and if so remove it.