Fix exception module not setting the HTTP response code

- Page->run now returns an updated response for use with Page->exit
- Remove now duplicated header setting in Page->run
- Remove now obsolete (and ineffective) HTTP return code setting from Module\Special\HTTPException->content
- Add HTTP response code and reason setting in BaseModule->run

src/Module/Special/HTTPException.php

@@ -126,8 +126,6 @@ class HTTPException
 	 */
 	public function content(\Friendica\Network\HTTPException $e): string
 	{
-		header($this->server['SERVER_PROTOCOL'] ?? 'HTTP/1.0' . ' ' . $e->getCode() . ' ' . $e->getDescription());
-
 		if ($e->getCode() >= 400) {
 			$this->logger->debug('Exit with error',
 				[