Delete obsolete file

The prompt before this point is '%n@%m:%~%#', so the deleted script no
longer does anything useful and is a potential issue for anyone using
an alternate theme.

zshrc.d/93-patch-oh-my-zsh-prompt.zsh

-# Patch %d in prompt to %~
-PS1=$(echo "$PS1" | sed -e 's/%d/%4~/')
-