6672.Bugfix

Restored documented pipenv update (no args) semantics of lock + sync. Since 2026.0.0, pipenv update only re-resolved Pipfile entries whose locked version no longer satisfied the Pipfile specifier, so relaxing a pin (e.g. urllib3 = "<2.7.0" → urllib3 = "*") would not pick up newer allowed releases — the lockfile silently stayed at the existing pin. pipenv update now routes through do_lock when no packages are given, re-resolving every Pipfile entry. The targeted pipenv update <pkg> path is unchanged.