Change admonitions

[jukent]

With the new sphinx theme, admonitions are called like

```{admonition} Info
:class: tip

In the above code example, we are extract ...

The HTML <div> ... version was causing the issues. This is isolated to these two files and doesn't require an overall theme adjustment.

Closes ProjectPythia/sphinx-pythia-theme#64

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[brian-rose]

Nice!

[brian-rose]

Link checker failure is unrelated, but we need to address that too.

[jukent]

Link checker failure is unrelated, but we need to address that too.

I just fixed one link, but there are two more that are failing to pass link-checker that aren't broken.

(core/datetime/datetime: line 200010) broken    https://ghrc.nsstc.nasa.gov/uso/ds_docs/vaiconus/vaiconus_dataset.html#a6 - HTTPSConnectionPool(host='ghrc.nsstc.nasa.gov', port=443): Max retries exceeded with url: /uso/ds_docs/vaiconus/vaiconus_dataset.html (Caused by NewConnectionError('<urllib3.connection.HTTPSConnection object at 0x7f5cbcc04830>: Failed to establish a new connection: [Errno 101] Network is unreachable'))
(core/datetime/datetime: line 200006) broken    https://ghrc.nsstc.nasa.gov/uso/ds_docs/vaiconus/vaiconus_dataset.html - HTTPSConnectionPool(host='ghrc.nsstc.nasa.gov', port=443): Max retries exceeded with url: /uso/ds_docs/vaiconus/vaiconus_dataset.html (Caused by NewConnectionError('<urllib3.connection.HTTPSConnection object at 0x7f5cbcd4ec60>: Failed to establish a new connection: [Errno 101] Network is unreachable'))
build finished with problems, 43 warnings.

[brian-rose]

Great!