Revise ZA relevant language entries

[lcjohnso]

Staging branch URL: https://pr-6732.pfe-preview.zooniverse.org

Matching zooniverse/pandora#661, update language entries relevant to South Africa, taking the following actions

• Remove duplicate entries.
• Make all -za entries general by removing country specification (non-specific versions were missing before).
• Edit labels for ZA-relevant entries to include standard/reference language name (matching ISO language name) and local names separated by "/" character. e.g., for xh, "Xhosa / isiXhosa"

Surpasses and replaces #6731.

Required Manual Testing

• Does the non-logged in home page render correctly?
• Does the logged in home page render correctly?
• Does the projects page render correctly?
• Can you load project home pages?
• Can you load the classification page?
• Can you submit a classification?
• Does talk load correctly?
• Can you post a talk comment?

Review Checklist

• Does it work in all major browsers: Firefox, Chrome, Edge, Safari?
• Does it work on mobile?
• Can you npm ci and app works as expected?
• If the component is in coffeescript, is it converted to ES6? Is it free of eslint errors? Is the conversion its own commit?
• Are the tests passing locally and on GitHub Actions?

Optional

• Have you replaced any ChangeListener or PromiseRenderer components with code that updates component state?
• If changes are made to the classifier, does the dev classifier still work?
• Have you resized and compressed any image you've added?
• Have you added in flow type annotations?
• Have you followed the Springer guidelines for commit messages?

[coveralls]

coverage: 57.233%. remained the same when pulling 630308c on za-lang-edit into eda3339 on master.

[eatyourgreens]

Can we please not use colonial names?

[lcjohnso]

As I wrote in the PR text, I'm opting to include both the official ISO Language Name and the local/native name. Including both names is useful -- it resolves possible confusion in the case of "Sesotho" -- Sesotho = Southern Sotho = st vs. Sesotho sa Leboa = Northern Sotho = nso.

[eatyourgreens]

The ISO name is not official. Can we use the names that we’ve been asked to use by people who speak these languages.

[eatyourgreens]

Also, ‘native name’????

[eatyourgreens]

Can we use the language names that we’ve been given by our colleagues in South Africa?

[eatyourgreens]

Here's the list of languages that we've been given:

• isiXhosa
• Sesotho
• Tshivenḓa
• Xitsonga
• isiZulu

If we could stick with those names, that would be great. If we must add the European names too, then we could maybe do something like 'Xitsonga / Tsonga' but I'm not sure what value the European names add to the project builder.