Use proper if comparison

lib/completion.zsh

@@ -58,7 +58,7 @@ zstyle ':completion:*:*:*:users' ignored-patterns \
 # ... unless we really want to.
 zstyle '*' single-ignored show
 
-if [ "x$COMPLETION_WAITING_DOTS" = "xtrue" ]; then
+if [[ $COMPLETION_WAITING_DOTS = true ]]; then
   expand-or-complete-with-dots() {
     echo -n "\e[31m......\e[0m"
     zle expand-or-complete