ci: fix broken jobs on Ubuntu 25.10 caused by switch to sudo-rs(1)

ci: fix broken jobs on Ubuntu 25.10 caused by switch to sudo-rs(1)

Ubuntu 25.10 has been released. One prominent change in this version of
Ubuntu is the switch to some Rust-based utilities. Part of this switch
is also that Ubuntu now defaults to sudo-rs(1).

Unfortunately, this breaks our CI because sudo-rs(1) does not support
the `--preserve-env` flag. Let's revert back to the C-based sudo(1)
implementation to fix this.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>