Because we use the --clean argument to `pg_dump`, the database backup
SQL file has many DROP commands that precede the section to restore the
tables and data. However, on instances with an empty database, these
DROP statements generate a lot of noise and make it difficult to filter
true error messages from noise.

In preparation of capturing error messages from stderr, we add this to
the backup commands to make it easier to flag real errors.

Reference: https://www.postgresql.org/docs/11/app-pgdump.html

Relates to https://gitlab.com/gitlab-org/gitlab/-/issues/36405