Filter out non-existent tasks from --graph

[gsong]

Which project is this feature idea for?

Turborepo

Describe the feature you'd like to request

It's great that we can generate task dependency graph. However, there's a lot of noise for non-existent tasks in there. Is there any way to filter those out?

Describe the solution you'd like

Generate a graph with only valid tasks shown.

Describe alternatives you've considered

I guess manually editing the dot file first?