[9.20] chg: ci: Exclude some RPZ files from long stress test artifacts

[9.20] chg: ci: Exclude some RPZ files from long stress test artifacts

This fixes 6f868853049769cd4c327acf32a8c1a7320daa06, that excluded files
only from short stress tests.

Validation jobs:
- [x] short - [#4756989](https://gitlab.isc.org/isc-projects/bind9/-/jobs/4756989/artifacts/browse/output/ns4/) -
- [x] long - [#4757196](https://gitlab.isc.org/isc-projects/bind9/-/jobs/4757196/artifacts/browse/output/ns4/)

Backport of MR !9522

Merge branch 'backport-mnowak/exclude-some-rpz-files-from-long-stress-tests-artifacts-9.20' into 'bind-9.20'

See merge request isc-projects/bind9!9538