In #283893 we realized that not only 6.7, but also testing is affected.
And with more stable kernels following, we'll probably want to test
against all of them whether Rust support is working fine. As long as
it's not the default at least, then we should probably move this to
`kernel-generic`.
Every kernel that's new enough to support `rust-out-of-tree-module` (and
`linux_testing`) is part of this text matrix.
