jack: Removed FIXME comment that has since been fixed.

src/audio/jack/SDL_jackaudio.c

@@ -333,8 +333,6 @@ static int JACK_OpenDevice(SDL_AudioDevice *device)
         return SDL_SetError("No physical JACK ports available");
     }
 
-    /* !!! FIXME: docs say about buffer size: "This size may change, clients that depend on it must register a bufsize_callback so they will be notified if it does." */
-
     // Jack pretty much demands what it wants.
     device->spec.format = SDL_AUDIO_F32;
     device->spec.freq = JACK_jack_get_sample_rate(client);