Fix compilation errors

[0-wiz-0]

When compiling apple-codesign-0.17.0 on NetBSD with rust-1.60.0, I got the following errors:

warning: unused import: `Decodable`
  --> apple-codesign/src/cryptography.rs:13:17
   |
13 |     der::{asn1, Decodable, Document, Encodable},
   |                 ^^^^^^^^^
   |
   = note: `#[warn(unused_imports)]` on by default

warning: field is never read: `data`
   --> apple-codesign/src/macho.rs:633:5
    |
633 |     data: &'a [u8],
    |     ^^^^^^^^^^^^^^
    |
    = note: `#[warn(dead_code)]` on by default

The patches fix them for me.

[indygreg]

The apple-codesign project was moved to https://github.com/indygreg/apple-platform-rs. If this change is still needed, please rebase this change onto that repo. (That repo is a fork of this one so a git rebase should work.)