Fix IntrospectionQuery type definition

[sobolevn]

TypedDict mangles private names as regular Python classes do. So, __schema name will become _IntrospectionQuery__schema instead. But, inline definition will preserve a correct name for the field. See python/cpython#129567

Found during python/mypy#16715

[Cito]

Thanks for reporting and the PR. Is this also a problem with current mypy versions? If yes, how can I provoke a typing error there?

[sobolevn]

Not until python/mypy#16715 is merged

[codspeed-hq]

CodSpeed Performance Report

Merging #234 will not alter performance

_{Comparing sobolevn:patch-1 (e5d09fa) with main (44334f3)}

Summary

✅ 14 untouched benchmarks

[Cito]

Looks good, but you need to silence the linter with # noqa: UP013 because it prefers class syntax, and add a small comment as explanation why we deviate from the class syntax here.

[Cito]

Now there are only mypy issues, probably because mypy has been updated and not related to this PR. Will fix them separately.