Unset `config_file` variable in oh-my-zsh.sh
Unset `config_file` variable in oh-my-zsh.sh

`config_file` variable will mess up with `cd` auto-complete command.

eg. I have a local dir named `Code`, and when I type `cd co<Tab>`,
config_file will show up, and doesn't make any sense...

larrylv/dotfiles,sakishum/dotfiles-2,sakishum/dotfiles-2,sakishum/dotfiles-2,larrylv/dotfiles