#838 Update Composer dev dependencies

[PANawkar]

Implemented:
dealerdirect/phpcodesniffer-composer-installer ^1.2
PHPUnit refresh constrained to ^8.5.x
yoast/phpunit-polyfills ^4.0
Updated composer.lock

Set config.platform.php to 7.2.24 to ensure compatibility with wp-env PHPUnit runs on PHP 7.2.

Deferred Updates
The following upgrades are deferred:
spatie/phpunit-watcher ^1.24
szepeviktor/phpstan-wordpress ^2
phpstan/phpstan ^2

These require PHP 8.1+ / Symfony 6, which introduces PHP 8-only syntax into vendor/ and breaks the current single-vendor, multi-PHP CI matrix.

[github-actions]

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Co-authored-by: PANawkar <pratiknawkar94@git.wordpress.org>
Co-authored-by: masteradhoc <masteradhoc@git.wordpress.org>

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[PANawkar]

Reopen this PR as upgrade dev dependencies is partially fixable.

[masteradhoc]

@PANawkar can you remove your adjustments to nonces from this PR? We'll check those in #833

[PANawkar]

@PANawkar can you remove your adjustments to nonces from this PR? We'll check those in #833

Yes, I’ve raised another PR with only the Composer changes.