Stop querying for done and all todo counts

What does this MR do and why?

Stop querying for done and all todo counts

We're now only querying and showing the pending todo count to alleviate some performance issues when fetching other counts that involve intensive database operations.

MR acceptance checklist

Please evaluate this MR against the MR acceptance checklist. It helps you analyze changes to reduce risks in quality, performance, reliability, security, and maintainability.

Screenshots or screen recordings

Before	After

How to set up and validate locally

1. Enable the todos_vue_application feature flag: echo "Feature.enable(:todos_vue_application)" | rails c.
2. Navigate to the Vue todos app: http://gdk.test:3000/dashboard/todos/vue.

Related to #499343 (closed)