Exclude historical entries from the dashboard

The 25 pre-2022 results imported from the original ClickHouse
benchmark page (and any future entries tagged "historical") stay in
the repository for archival purposes but are no longer rendered on
the website. generate-results.sh skips files where tags includes
"historical".

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: alexey-milovidov