SED command to delete last line in a remote host

Question

I have the following running one liner to delete last injected ED key from last line of authorized keys folder of a remote host.

sed -i '${/^\(ssh-ed25519\) \(.*\) \([A-Za-z][A-Za-z]*\.[A-Za-z][A-Za-z]*@hpe\.com\)$/d;}' .ssh/authorized_keys

I do a couple of operations after creating ED key and injecting it into remote host. Then I want to clear up as tear down step. However when I tried to run it by connecting to remote host it failed. I tried the following things:

ssh -T 'sh -c "sed command here"'  # too many single and double quotes, so I gave up

Then I tried removing T terminal and as well as "sh -c" command running part

ssh root@my_remote_host "sed -i '${/^\(ssh-ed25519\) \(.*\) \([A-Za-z][A-Za-z]*\.[A-Za-z][A-Za-z]*@hpe\.com\)$/d;}' .ssh/authorized_keys"

had this error:

sed: couldn't open temporary file .ssh/sedWC1YAQ: Read-only file system

I referred to this link but it also didn't help : Using SED in a ssh command on a remote node

I appreciate any help, and let me know if what I'm trying is a good way to apply.