Delete forgotten configuration file

The zsh-navigation-tools plugin is no longer used.

zshrc.d/56-plugin-zsh-navigation-tools.zsh

-
-# Bind ^A and ^z to zsh-navigation-tools
-#zle -N znt-cd-widget
-#bindkey "^A" znt-cd-widget
-#zle -N znt-kill-widget
-#bindkey "^Y" znt-kill-widget
-
-# Use instant selects
-znt_list_instant_select=1
-