TaskWikiChooseProject stop showing old projects

[yongli-abc]

Hi, currently :TaskWikiChooseProject shows all the projects, same as the output from taskwarrior projects.

However, I'd like to see only projects with active pending tasks, so the list is a bit shorter and cleaner.

This should be given by taskwarrior projects all.

[yongli-abc]

A quick fix is to add tw_extra_args in class SplitProjects