chore: Empty out config-spec/properties.yaml

product-config no longer reads this file, but it is kept (empty) because the
build/packaging process still expects it (it is COPYd into the operator image).
Mirrors trino-operator. To be removed entirely in a later cleanup.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: maltesander