ci: temporarily remove rust from Ubuntu This is for the purpose of getting an easy-to-use base for future development. The plan is: - that Debian will require trixie to enable Rust usage - that Ubuntu will backport 1.83 to its 22.04 and 24.04 versions (https://bugs.launchpad.net/ubuntu/+source/rustc-1.83/+bug/2120318) Marc-André is working on adding Rust to other CI jobs. Reviewed-by: Zhao Liu <zhao1.liu@intel.com> Link: https://lore.kernel.org/r/20250908105005.2119297-2-pbonzini@redhat.com Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>