Update submodule oh-my-zsh 76b8fc0...9378846

* oh-my-zsh 76b8fc0...9378846 (5):
  > zshrc: improve -256color suffix hack (look also at $COLORTERM)
  > zshrc: no noglob with ag alias
  > zshrc: drop vi-mode plugin
  > zshrc: pass through COLORTERM with ssh (via LC_MY_SSH_COLORTERM)
  > zshrc: extend TERM=$TERM-256color hack for TERM=screen