Remove legacy Spanish homepage

[niqjohnson]

Now that the updated Spanish homepage is launched, we can clean up the feature flag we were using for development and get rid of the legacy homepage code.

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Removals

• SPANISH_HOMEPAGE feature flag
• Legacy homepage template and content

How to test this PR

1. Make sure / and /es/ both render as they do in production

Notes and todos

• I poked around for any other legacy homepage bits, including tests, and didn't find any.
• There's probably a more compact way to specify the template in get_template, but I kind of like being explicit that only English and Spanish have a homepage, so I left them on separate lines—happy to revise if there's a better way, though.

Checklist

• PR has an informative and human-readable title
  • PR titles are used to generate the change log in releases; good ones make that easier to scan.
  • Consider prefixing, e.g., "Mega Menu: fix layout bug", or "Docs: Update Docker installation instructions".
• Changes are limited to a single goal (no scope creep)
• Code follows the standards laid out in the CFPB development guidelines
• Project documentation has been updated

[wpears]

🆒

[chosak]

Awesome -- one non-blocking suggestion.

[chosak]

For simplicity, we could remove this entire method in favor of a

template = "v1/home_page/home_page.html"

If someone were to create a HomePage with another language, they'd still get a (slightly less helpful) error message when this import statement failed.

If we did that we could remove these unit tests entirely as well.

[niqjohnson]

@chosak, good call, I simplified template selection and ditched the unit tests in 92ae773. I initially liked being explicit about which languages we had a homepage in, but thinking about it more, if the end goal is to move the content into Wagtail, it makes more sense to simplify things as much as possible now. I've re-requested reviews.

[wpears]

Thanks to @chosak for the simplification