use nightly built wheels for `astropy`

[zacharyburnett]

this PR attempts to solve the issue with building astropy in the Jenkins job (https://plwishmaster.stsci.edu:8081/blue/organizations/jenkins/RT%2Fcalcos/detail/calcos/1622/pipeline), by using the nightly-built dev wheels

[codecov[bot]]

Codecov Report

Base: 87.17% // Head: 87.17% // No change to project coverage :thumbsup:

Coverage data is based on head (3c108ee) compared to base (78cca9f). Patch has no changes to coverable lines.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #220 +/- ## ======================================= Coverage 87.17% 87.17% ======================================= Files 17 17 Lines 1333 1333 ======================================= Hits 1162 1162 Misses 171 171 ``` | Flag | Coverage Δ | | |---|---|---| | unit | `87.17% <ø> (ø)` | | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=spacetelescope#carryforward-flags-in-the-pull-request-comment) to find out more. Help us with your feedback. Take ten seconds to tell us [how you rate us](https://about.codecov.io/nps?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=spacetelescope). Have a feature suggestion? [Share it here.](https://app.codecov.io/gh/feedback/?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=spacetelescope)

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