[954] Fix $recursiveAnchor in schema to match spec

[ssilverman]

The spec allows values of false. This fixes the schema to match the spec.

Closes #954

[ssilverman]

See https://json-schema.org/draft/2019-09/json-schema-core.html#rfc.section.8.2.4.2.2:

If this keyword is set to false, the base URI is unchanged.

Also, the spec doesn't require the value to be true.

[Relequestual]

Thanks!
Could you also update the 2019-09 meta schema please?
Once done, I'll merge.

[karenetheridge]

Could you also update the 2019-09 meta schema please?

what update is needed? $recursiveAnchor isn't defined in the main meta-schema document.

[Relequestual]

What appears on the website for fetching, the schemas for previous versions are included via git submodule.
This can be eased if the branch on here gets updated with the fix too.
This also applies for #900 but I just didn't remember.

[Relequestual]

I guess what we actually need is a second PR, because this one can be merged.

[karenetheridge]

PR created in #968.