docs: fix misplaced prepositional phrase error in useTransition doc content

[mehmetmalli]

I noticed a very small grammatical error while reading the useTransition hook docs and wanted to correct it.

Text from the docs:

To give the user feedback about in-progress Transitions, to `isPending` state switches to `true` at the first call to `startTransition`, and stays `true` until all Actions complete and the final state is shown to the user.

to isPending state part in this sentence is not grammatically correct, I think the original author meant the isPending state so I made the change.