warning: unused import: `FromHex`

When compiling current `master` (i.e. c86a143) I see the following warning:

```rust
warning: unused import: `FromHex`
 --> src/bin/hal/cmd/miniscript.rs:2:32
  |
2 | use bitcoin::hex::{DisplayHex, FromHex};
  |                                ^^^^^^^
  |
  = note: `#[warn(unused_imports)]` on by default
```