Add support for Python version 3.13 to include/prereq-build.mk.
One of the reasons for this change is that
Ubuntu 25.04 ships with Python 3.13 as default version.
Let's support it.
Signed-off-by: Kacper Ludwinski <kacper@ludwinski.dev>
Link: https://github.com/openwrt/openwrt/pull/20735
Signed-off-by: Christian Marangi <ansuelsmth@gmail.com>