fix(AppFramework): Fix error message about 204 not allowing custom headers

[provokateurin]

Summary

204 does allow custom headers, only 304 forbids them:

server/lib/public/AppFramework/Http/Response.php

Lines 208 to 218 in 1d5d8d4

	if ($this->status === Http::STATUS_NOT_MODIFIED
	&& stripos($name, 'x-') === 0) {
	/** @var IConfig $config */
	$config = \OC::$server->get(IConfig::class);
	if ($config->getSystemValueBool('debug', false)) {
	\OC::$server->get(LoggerInterface::class)->error('Setting custom header on a 204 or 304 is not supported (Header: {header})', [
	'header' => $name,
	]);
	}
	}

For reference: nextcloud/openapi-extractor#111

Checklist

• Code is properly formatted
• Sign-off message is added to all commits
• Tests (unit, integration, api and/or acceptance) are included
• Screenshots before/after for front-end changes
• Documentation (manuals or wiki) has been updated or is not required
• Backports requested where applicable (ex: critical bugfixes)

[nickvergessen]

https://github.com/symfony/symfony/blob/7.1/src/Symfony/Component/HttpFoundation/Response.php#L246-L249
Symfony also only removes the content related headers, so others seem okay.

[nickvergessen]

/backport to stable29