Fix wrong comment

src/main/java/com/kdanmobile/reader/copyfile/CopyFileViewModel.kt

@@ -21,7 +21,7 @@ import java.lang.Exception
  * 3. if the application has no permission,
  *          send Event.Failed(destination path, FileNotFoundException) and delete the destination file
  * 4. if an IOException is thrown during copying,
- *          send Event.Failed(destination path, FileNotFoundException) and delete the destination file
+ *          send Event.Failed(destination path, IOException) and delete the destination file
  * 5. otherwise, when CopyFileViewModel finishes copying file,
  *          call onCopySuccess() to send Event.Success(destination path)
  *