E325 削除時の権限拒否エラー

Linux Mintから次のメッセージを受け取りました：

325: ATTENTION
Found a swap file by the name "/etc/default/.grub.swp"
          owned by: root   dated: Fri Mar 29 17:37:00 2024
         file name: /etc/default/grub
          modified: YES
         user name: root   host name: ilugu-ThinkPad-X220
        process ID: 22737
While opening file "/etc/default/grub"
             dated: Fri Mar 29 18:02:31 2024
      NEWER than swap file!

(1) Another program may be editing the same file.  If this is the case,
    be careful not to end up with two different instances of the same
    file when making changes.  Quit, or continue with caution.
(2) An edit session for this file crashed.
    If this is the case, use ":recover" or "vim -r /etc/default/grub"
    to recover the changes (see ":help recovery").
    If you did this already, delete the swap file "/etc/default/.grub.swp"
    to avoid this message.
"/etc/default/grub" 33 lines, 1209 bytes

削除しようとしましたが、常に出力が表示されます。

rm /etc/default/.grub.swp

rm: remove write-protected regular file '/etc/default/.grub.swp'? y
rm: cannot remove '/etc/default/.grub.swp': Permission denied