Responses with 204 and 304 should be empty

[nickvergessen]

Neither are custom headers allowed:
https://github.com/nextcloud/server/blob/066f6ef16c7adb365b8c260ea6f06906ab63724e/lib/public/AppFramework/Http/Response.php#L208-L218

nor can those pages have a body:
https://github.com/nextcloud/server/blob/747aeded9d3ed08f3dc1ee348a7b8667c0091651/lib/private/AppFramework/OCS/BaseResponse.php#L108-L114

But Talks 304:
https://github.com/nextcloud/spreed/blob/99cafa2ceb247aa5541cc80ca3b4fcbd9d07c91d/src/types/openapi/openapi.ts#L1773-L1786

And Notifications 204:
https://github.com/nextcloud/notifications/blob/9a345d8bc5c5d7dcf2adf98c0cf568489995a7ea/openapi.json#L266-L302

report headers and bodies