The only thing it does not change a bootstrapping node to become a voter
in case the cluster does not support limited voters feature. But the
feature was introduced in 2025.2 and direct upgrade from 2025.1 to
version newer than 2026.1 is not supported. But even if such upgrade is
done the removed code has affect only during bootstrap, not during
regular boot.
Also remove the upgrade test since after the patch suppressing the
feature on the first boot will no longer behave correctly.