Fix example of json-chema README.md

[satoshionoda]

the example was not working as the property name model is a reserved keyword.

[AlitzelMendez]

thanks for your pull request! the change looks good! but the change on packages/json-schema/README.md is missing, please run pnpm regen-docs on repo root and after that it should be ready!
thanks again!

[chrisradek]

Thank you for submitting this PR!

The README.md is generated by running npm run regen-docs from inside packages/json-schema. This is the file where the property name should be changed:
https://github.com/microsoft/typespec/blob/main/packages/json-schema/.tspd/docs/usage.md

Note: In your original change, you updated make to maker, but I think this should remain make since it's common in the context of automobiles to refer to a car's model, make, and year. Definitely understand the model rename though given it's a reserved word.