rust gtk4 autopkgtests failing

[Jeremy Bícha]

The rust-gdk4-sys and rust-gtk4-sys autopkgtests are failing with gtk 4.12.0

https://autopkgtest.ubuntu.com/packages/r/rust-gdk4-sys/mantic/amd64
https://autopkgtest.ubuntu.com/packages/r/rust-gtk4-sys/mantic/amd64

These 2 packages only have 2 tests, and the failing one is cross_validate_constants_with_c

GTK4 is still under heavy development so there are going to be new constants added in new major releases. It should be possible for us to update GTK4 before we update the Rust crates.

Therefore, we are disabling that autopkgtest in Debian (and syncing to Ubuntu).

Other Info
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We do still plan to update the Rust crates to the GNOME 45 series for Ubuntu 23.10 but it's a big transition (approx 45 packages) that we aren't ready for today.

We weren't affected by this issue before because the tests were marked as flaky until the 0.6 upload a few weeks ago.

The test isn't run at build time and there are no known build test failures because of this issue.

I am filing this bug for tracking to prevent others from having to figure this out.