[PRQ#45059] Deletion Request for ros-build-tools-py3

MarsSeed [1] filed a deletion request for ros-build-tools-py3 [2]: Orphan package from 2020; upstream discontinued since same year. [a] The successor utility is ros-build-tools, available on AUR. All maintained ROS packages already depend on the latter. The currently supported ROS Noetic release only supports Python3; this older build tool was only used when there were both Python2 and Python3 packages in the earlier, now EOL releases. [a]: https://github.com/ros-melodic-arch/ros-build-tools-py3 [1] https://aur.archlinux.org/account/MarsSeed/ [2] https://aur.archlinux.org/pkgbase/ros-build-tools-py3/