Edit language list, remove dialect specificity

[lcjohnso]

Follows https://github.com/zooniverse/pandora/pull/848, moving toward a standard of using only two-character language codes (without dialect specification) in almost all cases.

Note: along with merge, a small amount of data cleanup is necessary for existing translations (i.e., fil-ph, nso-za, tn-za, xh-za, zu-za) to drop dialect codes and make compatible with newly revised language list.

Staging branch URL: https://pr-7134.pfe-preview.zooniverse.org

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?

[coveralls]

coverage: 56.969%. remained the same when pulling 1ea8af9a8fb1676f899d54ad921e68ccf1722878 on simple-lang-list into 5150a5ea4ecaee19bcf74327321a3bd659d5d391 on master.