Drop temporary index on ci builds
What does this MR do?
This drops a temporary index we don't need/use anymore. See #295477 (closed) for details.
Between 2020-12-23 and 2021-01-06, the index hasn't been used on GitLab.com (we used select * from pg_stat_user_indexes where indexrelname = 'tmp_build_stage_position_index'
to check). For details see the linked issue.
Does this MR meet the acceptance criteria?
Conformity
Edited by Grzegorz Bizon