Remove nonreal values from the schema

[queengooborg]

This PR removes nonreal (true and null) values from the BCD schema entirely. This follows the removal of all nonreal values throughout BCD, finalizing the process.

Note: this PR will fail until all the remaining nonreal values have been removed.

Fixes openwebdocs/project#206.

[danielhjacobs]

Fixes mdn/yari#11257 by making it a non-issue.

[queengooborg]

This is now ready to go, whoo!

I've also now labeled this as a major semver bump as this is a potentially breaking change. I thought about it a bit and I realized that TypeScript users may suffer compiling errors if their code expects nonreal values, so to play it safe, I feel this should not be a minor or patch release. (Additionally, it's big news too!)

[caugner]

I agree that this would be a breaking change requiring a major bump, but I would like if we could combine it with other breaking changes we may be thinking about.

Edit: Additionally, I'm wondering if it could make sense to keep nonreal values in the schema, but "just" disallow them for the current browsers we have, so that other browsers or engines could be added more easily in the future. Then again, maybe it's sufficient to use version ranges for that case?

[danielhjacobs]

Then again, maybe it's sufficient to use version ranges for that case?

Note that according to #24293 (comment), @queengooborg is working to eliminate ranges too.

[queengooborg]

I think that ranges would be sufficient for any new browsers we add to BCD, as all "true" values can be expressed in ranges already. There wouldn't be a way to express "null", but our closest option would be to set the feature to "false" and correct it later if we find that the browser does support it. With the efforts that have gone into the mdn-bcd-collector, the majority of our data would be automatically maintained and updated for new browsers, so I feel we're already set there!

I am working on replacing all ranges with exact version numbers as well, but that's a slow process so it'll be a while before ranges are removed!