Delete upstream branch

[ignatenkobrain]

Is your feature request related to a problem? Please describe.

As now gitui supports creation/deletion of branches, I'm missing functionality to actually delete branches from the remote (git push --delete <remote> <branch>)

Describe the solution you'd like

In the list of remote branches, deleting should actually push deletion.

Describe alternatives you've considered

I did not find any.

Additional context

Right now deleting of the branch in "remote" tab just deletes local reference to a branch and next "fetch" will bring it back.
Add any other context or screenshots about the feature request here.

[extrawurst]

Duplicate of #622 right?

[ignatenkobrain]

Oh, it seems so.