Bump MSRV to 1.93

[oech3]

Next Ubuntu LTS adopted Rust 1.93:
#9533 (comment)

Also this is needed for NetBSD CI #11470 (comment)

[Ecordonnier]

The next yocto LTS version (released in April 2026) will use rust 1.94, so an update to 1.93 would be OK for yocto consumers of uutils-coreutils.

[xtqqczze]

OK to bump?

I don't think there's a hurry? Let's wait Ubuntu 26.04 is released on 2026-04-23, or at least until Ubuntu for Developers | Available Rust versions documentation is updated.

#9533 (comment)

[xtqqczze]

Also this is needed for NetBSD CI #11470 (comment)

We don't need to bump MSRV for this.

at least until Ubuntu for Developers | Available Rust versions documentation is updated.

Issue opened: canonical/ubuntu-for-developers-docs#108