Audio: Apply inert directly instead of wrapping in Disabled

[Mamaduka]

What?

The Audio block's edit component wrapped the <audio> in a Disabled component to prevent playback when the block isn't selected. The only behavior needed here is inert, so apply it directly to the <audio> element instead.

This mirrors the same change made for the Video block in #79371.

Benefits:

• Removes an extra DOM node, so editor markup matches the frontend (save) output: <figure> -> <audio>.
• Drops the Disabled dependency and its unused styles/context for this block.

Testing Instructions

1. Open a post or page.
2. Add the Audio block and select an audio file.
3. With controls enabled and the block deselected, clicking the audio
   should not play it or focus the controls.

Testing Instructions for Keyboard

Same.

[github-actions]

Size Change: +7 B (0%)

Total Size: 7.51 MB

📦 View Changed

Filename	Size	Change
build/scripts/block-library/index.min.js	324 kB	+7 B (0%)

_{compressed-size-action}

[t-hamano]

LGTM 👍

[github-actions]

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Co-authored-by: Mamaduka <[email protected]>
Co-authored-by: t-hamano <[email protected]>

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