remove auto-update plugin

plugins/auto-update/init.zsh

@@ -1,13 +0,0 @@
-# Auto-update zsh if its over 6 hours old
-# Jonathan Dahan <jonathan@jedahan.com>
-
-# Take a look at the update-omz options in functions/
-
-if [ -f ~/.omz-update ]; then
-  # update if ~/.omz-update was modified over 6 hours ago
-  if [ ~/.omz-update(Nmh+6) ]; then
-    update-omz
-  fi
-else
-  update-omz
-fi