fix: ci: Allow unit tests to fail on AlmaLinux 8

The doh unit test has been timing out recently and we don't have a fix
for it yet. Mark it as warning rather than a hard failure, since it's a
known issue.

Related #5448

Merge branch '5448-allow-failure-unit-almalinux8-doh' into 'main'

See merge request isc-projects/bind9!10835