Make BaseApi->checkAllowedScope into an object method

- It isn't called from static contexts anymore

src/Module/Api/Twitter/DirectMessages/Inbox.php

@@ -34,7 +34,7 @@ class Inbox extends DirectMessagesEndpoint
 {
 	protected function rawContent(array $request = [])
 	{
-		BaseApi::checkAllowedScope(BaseApi::SCOPE_READ);
+		$this->checkAllowedScope(BaseApi::SCOPE_READ);
 		$uid  = BaseApi::getCurrentUserID();
 		$pcid = Contact::getPublicIdByUserId($uid);