Document HTML5 script,style theme support is deprecated

[sirreal]

HTML5 theme support script and style is no longer use by WordPress Core and does not convey relevant or accurate information.

Add a since annotation to indicate this.

Trac ticket: https://core.trac.wordpress.org/ticket/64442

[github-actions]

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[sirreal]

https://core.trac.wordpress.org/ticket/64442#comment:25:

Given how little html5 script support is apparently used outside of Core, I'm tempted to leave the behaviors of get_theme_support() and current_theme_supports() unchanged. I've described some of the difficulties I discovered on the linked PR.

This ticket can then close with some documentation that html5 script theme support is deprecated.

[github-actions]

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