Replace non-PEP 585 types in watch.py

[jrmccluskey]

typing.Tuple and typing.Iterable usages in watch.py are incorrect, this updates to the modern hint format.

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[Abacn]

Thanks!

[Abacn]

Are we going to have lint check for this kind of issues?

[jrmccluskey]

Are we going to have lint check for this kind of issues?

It should already be doing so, I'm not entirely sure how watch.py dodged this (and ruff picked it up locally, so I need to check what the blind spot is.) I'm separately updating the ruff version in #39531, I'll see if I need to make any configuration updates there