refactor: remove redundant copy method from CompressionEngine implementations

src/compression/program.rs

@@ -79,12 +79,6 @@ impl CompressionEngine for CompressionEngineProgram {
         Ok(Box::new(process.stdin.unwrap()))
     }
 
-    fn copy(&self, file_path: PathBuf, writer: &mut dyn Write) -> Result<()> {
-        let mut reader = self.open(file_path)?;
-        io::copy(&mut reader, writer)?;
-        writer.flush()?;
-        Ok(())
-    }
 }
 
 fn get_program_path(program: &str) -> Result<String> {