Fix media_player tests for Python 3.14.3

[edenhaus]

Breaking change

Proposed change

SSIA, refers to #162263

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• Dependency upgrade
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• This PR fixes or closes issue: fixes #
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[home-assistant]

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[Copilot]

Pull request overview

Adjusts the media_player test suite to be resilient to scheduling/timing differences introduced by Python 3.14.3 (per the referenced base-image/CI update), ensuring assertions observe the post-service-call state.

Changes:

• Add an explicit hass.async_block_till_done() after turning off the demo media player group to ensure the scheduled state write has been processed before asserting on state/attributes.

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