Beryl: tried to install adguard now free space gone

I was too quick when trying to install adguardhome on my Beryl router.
There was just enough space left to download the package but not enough to install.

The problem is now that the download ate all my free space and I want to delete the file to get back my free disk space.
I checked with SSH and found the file in usr/bin but cannot remove it:

root@GL-MT1300:/usr/bin# sudo rm AdGuardHome
rm: remove ‘AdGuardHome’? y
rm: can’t remove ‘AdGuardHome’: Read-only file system

With the command ls -al, I read:

-rw-r–r-- 1 root root 32112640 Aug 18 16:37 AdGuardHome

Does anyone know how can I remove this file again?