[zsh] revert unnecessary manpath fix

zsh/zshrc

@@ -2,14 +2,14 @@
 
 ZSH_DOTFILES="${0:h}"
 
-# add colon after MANPATH so that it doesn't overwrite system MANPATH
-export MANPATH="$MANPATH:"
-
 for script in functions path env plugins aliases palette theme; do
   source "$ZSH_DOTFILES/$script.zsh"
   source_if_exists "$ZSH_DOTFILES/custom/$script.zsh"
 done
 
+# add colon after MANPATH so that it doesn't overwrite system MANPATH
+MANPATH="$MANPATH:"
+
 command_exists rbenv && eval "$(rbenv init -)"
 
 BASE16_SHELL_profile_helper="$BASE16_SHELL/profile_helper.sh"