[pkg] Use “dependency package” instead of “virtual package” to describe python3-cubicweb-postgresql-support The term “virtual” was too imprecise and is not accepted for empty packages by Lintian anymore.

Tests: unittest
Depends:
 python3-cubicweb,
 @builddeps@,
 python3-pytest,
 python3-crypto, python3-psycopg2,
 postgresql, postgresql-plpython,
 firefox
Restrictions: allow-stderr, isolation-container