use list's --flat option for bash completion

completions/bash/tiempo-autocomplete.bash

@@ -5,7 +5,7 @@ _tiempo ()
   cmd="${COMP_WORDS[1]}"
 
   if [[ ( $cmd = s* || $cmd = d* || $cmd = k* ) && "$COMP_CWORD" = 2 ]]; then
-    COMPREPLY=($(compgen -W "$(echo "select distinct sheet from entries where sheet not like '\_%';" | t b)" $cur))
+    COMPREPLY=($(compgen -W "$(t l --all --flat)" $cur))
     return
   elif [[ "$COMP_CWORD" = 1 ]]; then
     CMDS="archive backend configure display edit in kill list now out resume sheet week month"