Update pubsub_client.py

[Iaw4tch]

Description

By default Pylance handles Callable as (...) -> Unknown. This is a minor fix for avoiding a reportUnknownMemberType error

Test code

I wrote such string:

self.page.pubsub.subscribe_topic("emphasis_hue", self._subscription_wrapper)

end ended up with Pylance error:

Type of "subscribe_topic" is partially unknown
Type of "subscribe_topic" is "(topic: str, handler: (...) -> Unknown) -> None" Pylance[reportUnknownMemberType]

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

Checklist

• I signed the CLA.
• I have performed a self-review of my own code.
• My code follows the style guidelines of this project.
• I have commented my code, particularly in hard-to-understand areas.
• My changes generate no new warnings.
• New and existing tests pass locally with my changes.
• I have made corresponding documentation changes, if applicable.
• I have added changelog entries for user-facing changes, if applicable.
• I have updated release guide pages and website/sidebars.yml for breaking changes, removals, and deprecations, if applicable.

Summary by Sourcery

Bug Fixes:

• Specify concrete Callable signatures for pubsub subscription handlers to resolve Pylance reportUnknownMemberType diagnostics.

[CLAassistant]

All committers have signed the CLA.

[sourcery-ai]

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