ci: ensure turbo-types schemas are in sync (#10609)
### Description
In https://github.com/vercel/turborepo/pull/10590, I edited the JSON
schema directly, which [isn't the right
way](https://github.com/vercel/turborepo/pull/10590#discussion_r2171962005).
This PR introduces a CI check that I (and others) can't make this sort
of mistake in the future.
### Testing Instructions
[This
commit](https://github.com/vercel/turborepo/pull/10609/commits/3108ad0c57bfbeccfb60b87e7115b3398444e1de)
shows a failure because I added a `test` key to the schema (and
malformatted it in the process).
