add type-var ignore for the recently introduced mypy error

[anilbey]

A new error introduced to mypy is detected in tornado's repository.

tornado (https://github.com/tornadoweb/tornado)

• tornado/queues.py:384: error: A function returning TypeVar should receive at least one argument containing the same Typevar
• tornado/queues.py:421: error: A function returning TypeVar should receive at least one argument containing the same Typevar

This PR adds ignore to that error.

Reference: https://github.com/python/mypy/pull/13166