Looks like your git repo was removed from oh-my-zsh? You can re-add the remote and update to the latest version of Zsh by running:
cd ~/.oh-my-zsh
git init # you've already done this step, so you can skip
git remote add origin https://github.com/ohmyzsh/ohmyzsh.git
git fetch
git reset --hard origin/master
After that, restart your terminal instance and you should be good to go.
