taskwarrior: update completion to latest version (dcdf712)

Fixes #8249

plugins/taskwarrior/_task

 #compdef task
 #
-# Copyright 2010 - 2016 Johannes Schlatow
+# Copyright 2010 - 2019 Johannes Schlatow
 # Copyright 2009 P.C. Shyamshankar
 #
 # Permission is hereby granted, free of charge, to any person obtaining a copy
@@ -24,7 +24,7 @@
 # https://www.opensource.org/licenses/mit-license.php
 #
 typeset -g _task_cmds _task_projects _task_tags _task_config _task_modifiers
-_task_projects=($(task _projects))
+_task_projects=(${(f)"$(task _projects)"})
 _task_tags=($(task _tags))
 _task_zshids=( ${(f)"$(task _zshids)"} )
 _task_config=($(task _config))