jack: return TRUE during init when failing to dlopen

If we return FALSE, that means the plugin won't be tried again,
even if jack is available afterwards.

Followup to 689dbd1fbe43f293d7a46d5fa0fe1ddcfbea50d6

Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/4507>

subprojects/gst-plugins-good/ext/jack/gstjack.c

@@ -106,7 +106,7 @@ plugin_init (GstPlugin * plugin)
 
   if (!gst_jack_load_library ()) {
     GST_WARNING ("Failed to load jack library");
-    return FALSE;
+    return TRUE;
   }
 
   ret |= GST_ELEMENT_REGISTER (jackaudiosrc, plugin);