iter: add kani proof for next_unchecked (#280)
#2142
| Job | Run time |
|---|---|
| 7m 18s | |
| -1s | |
| 7m 17s |
kani proof for next_unchecked (#280)
#2142
| Job | Run time |
|---|---|
| 7m 18s | |
| -1s | |
| 7m 17s |