[zsh] Use fc -r instead of fzf --tac to speed up loadtime (#1097)

Reference: http://zsh.sourceforge.net/Doc/Release/Shell-Builtin-Commands.html

> The flag -r reverses the order of the events

shell/key-bindings.zsh

@@ -59,8 +59,8 @@ bindkey '\ec' fzf-cd-widget
 fzf-history-widget() {
   local selected num
   setopt localoptions noglobsubst noposixbuiltins pipefail 2> /dev/null
-  selected=( $(fc -l 1 |
-    FZF_DEFAULT_OPTS="--height ${FZF_TMUX_HEIGHT:-40%} $FZF_DEFAULT_OPTS --tac -n2..,.. --tiebreak=index --bind=ctrl-r:toggle-sort $FZF_CTRL_R_OPTS --query=${(qqq)LBUFFER} +m" $(__fzfcmd)) )
+  selected=( $(fc -rl 1 |
+    FZF_DEFAULT_OPTS="--height ${FZF_TMUX_HEIGHT:-40%} $FZF_DEFAULT_OPTS -n2..,.. --tiebreak=index --bind=ctrl-r:toggle-sort $FZF_CTRL_R_OPTS --query=${(qqq)LBUFFER} +m" $(__fzfcmd)) )
   local ret=$?
   if [ -n "$selected" ]; then
     num=$selected[1]