zeroize: bump zeroize_derive dep to v1.4 (#1190)

This is useful for `-Z minimal-versions` to ensure derived code builds
without warnings on recent Rust versions, which complain about the
earlier custom derive:

```
error: non-local `impl` definition, `impl` blocks should be written at the same level as their item
```

Author: tarcieri

zeroize/Cargo.toml

@@ -20,7 +20,7 @@ rust-version = "1.85"
 
 [dependencies]
 serde = { version = "1.0", default-features = false, optional = true }
-zeroize_derive = { version = "1.3", path = "../zeroize_derive", optional = true }
+zeroize_derive = { version = "1.4", path = "../zeroize_derive", optional = true }
 
 [features]
 default = ["alloc"]