Unit test GraphQueue class

[QMalcolm]

Housekeeping

• I am a maintainer of dbt-core

Short description

As part of our Robust Testing Initiative we want to create generalized fixtures for our unit tests to make writing unit tests easier. To that end we want to add or update unit some unit tests to utilize the new fixture. Currently the GraphQueue class is not unit tested at all. We could unit test by reusing the DiGraph fixture created in #9871.

Acceptance criteria

• There are unit tests for the GraphQueue class

Suggested Tests

The work is the tests

Impact to Other Teams

None

Will backports be required?

Narp

Context

[ChenyuLInx]

This should include testing the public interfaces.

[ChenyuLInx]

The work @MichelleArk(Thanks!) did in #10129 accomplished this ticket.