fixed autojump: autocompletion works with homebrew again

plugins/autojump/autojump.plugin.zsh

-if [ $commands[autojump] ]; then # check if autojump is
+if [ $commands[autojump] ]; then # check if autojump is installed
   if [ -f /usr/share/autojump/autojump.zsh ]; then # debian and ubuntu package
     . /usr/share/autojump/autojump.zsh
   elif [ -f /etc/profile.d/autojump.zsh ]; then # manual installation