ports-mgmt/pkg_replace: Update to 20231008

ChangeLog: https://github.com/kdeguchi/pkg_replace/releases/tag/20231008

*Check the pkg command if it is installed or not.
*Improved FLAVOR handling when installing new packages.
See example section in pkg_replace(1).

PR: 274390
Reported by: kdeguchi@sz.tokoha-u.ac.jp (maintainer)