Defer retrieval of GitHub API key to runtime

[AetherUnbound]

Description

Follow up to WordPress/openverse#1457 and #937, this moves the last top-level Variable.get call into a template so that we are no longer performing Variable retrievals during DAG parse time (but rather waiting until runtime to perform the value retrieval).

Testing Instructions

1. Ensure that the DAG runs fine locally
2. (Optional) check that the task's "Rendered Template" shows the GitHub PAT value correctly interpolated into the op_kwargs

Checklist

• My pull request has a descriptive title (not a vague title like
  Update index.md).
• My pull request targets the default branch of the repository (main) or
  a parent feature branch.
• My commit messages follow best practices.
• My code follows the established code style of the repository.
• I added or updated tests for the changes I made (if applicable).
• I added or updated documentation (if applicable).
• I tried running the project locally and verified that there are no visible
  errors.
• I ran the DAG documentation generator (if applicable).

Developer Certificate of Origin

Developer Certificate of Origin

Developer Certificate of Origin
Version 1.1

Copyright (C) 2004, 2006 The Linux Foundation and its contributors.
1 Letterman Drive
Suite D4700
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Everyone is permitted to copy and distribute verbatim copies of this
license document, but changing it is not allowed.


Developer's Certificate of Origin 1.1

By making a contribution to this project, I certify that:

(a) The contribution was created in whole or in part by me and I
    have the right to submit it under the open source license
    indicated in the file; or

(b) The contribution is based upon previous work that, to the best
    of my knowledge, is covered under an appropriate open source
    license and I have the right under that license to submit that
    work with modifications, whether created in whole or in part
    by me, under the same open source license (unless I am
    permitted to submit under a different license), as indicated
    in the file; or

(c) The contribution was provided directly to me by some other
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    it.

(d) I understand and agree that this project and the contribution
    are public and that a record of the contribution (including all
    personal information I submit with it, including my sign-off) is
    maintained indefinitely and may be redistributed consistent with
    this project or the open source license(s) involved.

[stacimc]

LGTM! Sorry for the delay, @AetherUnbound -- I tested this several days ago and must not have finished the review 😅

[openverse-bot]

Based on the low urgency of this PR, the following reviewers are being gently reminded to review this PR:

@obulat
This reminder is being automatically generated due to the urgency configuration.

Excluding weekend¹ days, this PR was updated 5 day(s) ago. PRs labelled with low urgency are expected to be reviewed within 5 weekday(s)².

@AetherUnbound, if this PR is not ready for a review, please draft it to prevent reviewers from getting further unnecessary pings.

Footnotes

1. Specifically, Saturday and Sunday. ↩

2. For the purpose of these reminders we treat Monday - Friday as weekdays. Please note that the that generates these reminders runs at midnight UTC on Monday - Friday. This means that depending on your timezone, you may be pinged outside of the expected range. ↩

[zackkrida]

Thanks for the clear test instructions. LGTM!