Fix typo in ceval.c

[zhanpon]

There are no functions named _PyEval_InitPendingCalls() nor _PyEval_FiniPendingCalls():

$ git rev-parse HEAD
78a85a34ea2583b8489eeafba5b2018fa2048a4d

$ git grep _PyEval_InitPendingCalls
Python/ceval.c:    /* Ensure that _PyEval_InitPendingCalls() was called

$ git grep _PyEval_FiniPendingCalls
Python/ceval.c:       and that _PyEval_FiniPendingCalls() is not called yet. */

I suppose the intended functions are _PyEval_InitState() and _PyEval_FiniState(). FYI, the original comment is introduced in dda5d6e of #19436.

(I belive this PR doesn't require an issue)

[zhanpon]

@vstinner The comment was introduced in your pull request #19436. Would you mind taking a look?