Updated Withings Sync details

- changed Callback URL to Github pages
- (no need to change client_id and cunsumer_secret)
- In the App, changed the env from Dev to Production (this should help to avoid _max 10 users_ error)

withings_sync/config/withings_app.json

@@ -1,5 +1,5 @@
 {
-    "callback_url": "https://wieloryb.uk.to/withings/withings.html",
+    "callback_url": "https://jaroslawhartman.github.io/withings-sync/contrib/withings.html",
     "client_id": "183e03e1f363110b3551f96765c98c10e8f1aa647a37067a1cb64bbbaf491626",
     "consumer_secret": "a75d655c985d9e6391df1514c16719ef7bd69fa7c5d3fd0eac2e2b0ed48f1765"
-}
+}