Remove the obsolete publications/ directory

in_production.bib, mock_papers.bib, templates.bib, templates_obsolete.bib and
publications.qmdold are not referenced by the site nor read by computo-publish
(which extracts BibTeX from each article page); untouched since March 2025.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

Author: jchiquet