check-targets scheduled-only CI job always fails

eg https://gitlab.torproject.org/tpo/core/arti/-/jobs/592219

This seems to be something to do with Windows. It is outputting stuff like this:

   |
53 |             borrow = sbb(borrow, (*a).into(), 0, a);
   |                                  +  ++++++++
error[E0308]: arguments to this function are incorrect
  --> /usr/local/cargo/registry/src/index.crates.io-6f17d22bba15001f/num-bigint-0.4.5/src/biguint/subtraction.rs:75:18
   |
75 |         borrow = sbb(borrow, *ai, *bi, bi);
   |                  ^^^         ---  ---  -- expected `&mut u64`, found `&mut u32`
   |                              |    |
   |                              |    expected `u64`, found `u32`
   |                              expected `u64`, found `u32`
   |
   = note: expected mutable reference `&mut u64`
              found mutable reference `&mut u32`
note: function defined here
  --> /usr/local/cargo/registry/src/index.crates.io-6f17d22bba15001f/num-bigint-0.4.5/src/biguint/subtraction.rs:13:4

I notice that the runes in the maint/cargo_check_target script do not appear to pass --locked.

I looked at the upstream repos for num-bigint, and bitflags, and there didn't seem to be any relevant recent tickets or MRs.

AFAICT this last passed on 30.4.24.