apt update not working on Ubuntu 21.04

Hello,

I would like to update my ubuntu 21.04 droplet but when I do :

apt update

I have this error :

root@ubuntu-s-1vcpu-1gb-lon1-01:~# apt update
Hit:1 http://old-releases.ubuntu.com/ubuntu hirsute-security InRelease
Get:2 https://download.docker.com/linux/ubuntu hirsute InRelease [48.9 kB]                                                               
Ign:3 http://mirrors.digitalocean.com/ubuntu hirsute InRelease                                                                           
Ign:4 http://mirrors.digitalocean.com/ubuntu hirsute-updates InRelease
Hit:5 https://repos-droplet.digitalocean.com/apt/droplet-agent main InRelease
Ign:6 http://mirrors.digitalocean.com/ubuntu hirsute-backports InRelease
Err:7 http://mirrors.digitalocean.com/ubuntu hirsute Release
  404  Not Found [IP: 172.67.148.71 80]
Err:8 http://mirrors.digitalocean.com/ubuntu hirsute-updates Release
  404  Not Found [IP: 172.67.148.71 80]
Err:9 http://mirrors.digitalocean.com/ubuntu hirsute-backports Release
  404  Not Found [IP: 172.67.148.71 80]
Reading package lists... Done
E: The repository 'http://mirrors.digitalocean.com/ubuntu hirsute Release' no longer has a Release file.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.
N: See apt-secure(8) manpage for repository creation and user configuration details.
E: The repository 'http://mirrors.digitalocean.com/ubuntu hirsute-updates Release' no longer has a Release file.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.
N: See apt-secure(8) manpage for repository creation and user configuration details.
E: The repository 'http://mirrors.digitalocean.com/ubuntu hirsute-backports Release' no longer has a Release file.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.
N: See apt-secure(8) manpage for repository creation and user configuration details.

Ubuntu 21.04 (GNU/Linux 5.11.0-49-generic x86_64)