chore: repair clippy lint

Clippy recommends adding the explicit truncate on this file creation.

src/cmd/export.rs

@@ -287,6 +287,7 @@ fn run(matches: &clap::ArgMatches) -> Result<()> {
  let mut file = std::fs::File::options()
  .write(true)
  .create(true)
+ .truncate(true)
  .open(output_dir.join(&patchfile_name))
  .with_context(|| format!("opening {patchfile_name}"))?;
  file.write_all(&specialized)?;