removing /etc/nginx/sites-enabled/default.save

Hello, I renewed my SSL certificate via let’s encrypt. I always could do it with the configure files that I had however this time I could not run nginx ([emerg] 4026#4026: duplicate listen options for [::]:80 in /etc/nginx/sites-enabled/default.save:31)and I found the problem is related to perhaps new nginx version that is updated by Digital Ocean automatically. I needed to remove default_server ipv6only=on from /etc/nginx/sites-enabled/default then I noticed that still I could not run nginx with the same errors. Then I noticed that I need to basically delete /etc/nginx/sites-enabled/default.save How could I delete this file? rm: remove write-protected regular file ‘/etc/nginx/sites-enabled/default.save’? y rm: cannot remove ‘/etc/nginx/sites-enabled/default.save’: Permission denied I logged in via ssh connection with keys. By the way I could edit the file with nono and remove default_server ipv6only=onsection and now it is working fine. By the way, what exactly default_server ipv6only=on does and if one day I want to delete ‘/etc/nginx/sites-enabled/default.save’ how should I get ride of permission denied? thanks