fix: remove circular dependency checks

[eddyerburgh]

The checks currently fail for lots of edge cases:

stubs: {
  UnreadState: '<div data-stub-unread-state v-bind="$props"><slot/></div>',
  UnreadState: '<div>unread-state</div>',
}

This removes checks for circular dependencies when using the stubs option. This was simple error handling, but I believe the logic to implement it effectively is substantial. For the moment, we should remove the check

[Akryum]

@eddyerburgh I'm not sure the PR removes the checks in the code itself (you seem to only have changed the tests).

[eddyerburgh]

Ah sorry, I was in a rush.

This has been removed in another PR, but it won't be released for another week or so (until beta.16).