How can I delete a repository on github with an arrow?

When it is a normal directory, I can delete it through the Github visual interface, but when there is an arrow in the repository, it doesn't work.

I would not like to delete my last commit. How do I do this in the Github interface?

An arrow means "gitlink", a SHA1 reference to another repository.
If you have a .gitmodules file in the same repository, that folder would have a '@': submodule, but I suspect it is not the case here.

A gitlink is not a folder, but a special entry in the index, recording the tree SHA1 of a nested repository.

It is best deleted locally:

git clone
git rm --cached algortimos-eleicao # no trailing /
git commit -m "remove gitlink"
git push 

That will create a new commit which only remove that "folder".
(git revert does not necessarily work here, since I don't know what your last commit was)