Fix cfail tests

Author: sosthene-nitrokey

cfail/ui/not-send.stderr

@@ -72,19 +72,19 @@ error[E0277]: `*const ()` cannot be sent between threads safely
 22 |     is_send::<Vec<NotSend, 4>>();
    |               ^^^^^^^^^^^^^^^ `*const ()` cannot be sent between threads safely
    |
-   = help: within `heapless::Vec<PhantomData<*const ()>, 4>`, the trait `Send` is not implemented for `*const ()`
+   = help: within `heapless::vec::VecInner<[MaybeUninit<PhantomData<*const ()>>; 4]>`, the trait `Send` is not implemented for `*const ()`
 note: required because it appears within the type `PhantomData<*const ()>`
   --> $RUST/core/src/marker.rs
 note: required because it appears within the type `ManuallyDrop<PhantomData<*const ()>>`
   --> $RUST/core/src/mem/manually_drop.rs
 note: required because it appears within the type `MaybeUninit<PhantomData<*const ()>>`
   --> $RUST/core/src/mem/maybe_uninit.rs
    = note: required because it appears within the type `[MaybeUninit<PhantomData<*const ()>>; 4]`
-note: required because it appears within the type `Vec<PhantomData<*const ()>, 4>`
+note: required because it appears within the type `VecInner<[MaybeUninit<PhantomData<*const ()>>; 4]>`
   --> $HEAPLESS/src/vec.rs
    |
-   | pub struct Vec<T, const N: usize> {
-   |            ^^^
+   | pub struct VecInner<B: ?Sized + VecDrop> {
+   |            ^^^^^^^^
 note: required by a bound in `is_send`
   --> ui/not-send.rs:14:8
    |