TST: Refactored bounding box broke linkcheck, Azure Pipelines #12283

#11930 broke two things in this package CI. I milestoned this issue because these should be fixed before release. cc @WilliamJamieson and @nden

1. linkcheck in cron job, see https://github.com/astropy/astropy/runs/3993278320?check_suite_focus=true
2. Azure Pipelines, see the sdist job. There are other errors but two of them are from bounding box.