Repair wp/6.9 branch Actions: Guard setAccessible() calls for PHP 8.5 - #82876

Part of #82785.

What?

Guard every remaining unguarded ReflectionMethod::setAccessible() / ReflectionProperty::setAccessible() call in the PHPUnit test suite with if ( PHP_VERSION_ID < 80100 ), in:

• phpunit/class-wp-theme-json-resolver-test.php (5 occurrences)
• phpunit/blocks/class-wp-navigation-block-renderer-test.php (5 occurrences)
• phpunit/class-wp-theme-json-test.php (8 occurrences)
• phpunit/class-wp-duotone-test.php (4 occurrences)
• phpunit/blocks/render-block-rss-test.php (1 occurrence)

23 occurrences total.

Why?

PHP 8.5 deprecates ReflectionMethod::setAccessible() and ReflectionProperty::setAccessible() — they've had no effect since PHP 8.1, since reflection can access private/protected members without the call from that version onward. This project's PHPUnit configuration turns deprecation notices into test errors, so the PHP 8.5 leg added by #82874, directly below, fails every test that makes one of these calls, with:

Method ReflectionProperty::setAccessible() is deprecated since 8.5, as it has no effect since PHP 8.1

The call is still genuinely required on PHP < 8.1, which gutenberg.php continues to support down to PHP 7.4 — reflection cannot access a private/protected member on those versions without it. Version-gating with PHP_VERSION_ID < 80100 is therefore the correct fix for both ends of the supported PHP range, not a workaround: it keeps the call in effect where it's needed and silences the deprecation everywhere it's redundant.

Trunk hit and fixed the identical issue in commit 3fded09 (WordPress/gutenberg#79260, "CI: Run PHP unit tests on PHP 8.4 and 8.5"), landed 2026-06-17 — well after wp/6.9 branched, so it never made it back here on its own.

How?

This PR ports trunk's fix, cherry-pick style, adapted to wp/6.9's current line numbers (which have drifted from trunk's). The wrapping pattern is identical to trunk's:

if ( PHP_VERSION_ID < 80100 ) {
	$reflection->setAccessible( true );
}

One difference from a literal cherry-pick: trunk's diff for commit 3fded09 only shows 2 of class-wp-duotone-test.php's 4 setAccessible() occurrences, since the other 2 had already been guarded by an earlier, separate trunk commit before wp/6.9 branched off. On wp/6.9, all 4 were still unguarded, so all 4 are guarded here.

No other content in these files was changed.

Use of AI Tools

This PR was created by Claude Code under my supervision. All code should be treated as AI-produced and not yet reviewed by a human until this PR is marked Ready for Review.