Birthdays: Fix tests, add test for misskey

Signed-off-by: marcin mikołajczak <git@mkljczk.pl>

test/pleroma/web/mastodon_api/update_credentials_test.exs

@@ -387,7 +387,7 @@ defmodule Pleroma.Web.MastodonAPI.UpdateCredentialsTest do
         })
 
       assert user_data = json_response_and_validate_schema(res, 200)
-      assert user_data["pleroma"]["source"]["show_birthday"] == true
+      assert user_data["source"]["pleroma"]["show_birthday"] == true
     end
 
     test "emojis in fields labels", %{conn: conn} do