[release-notes] Add XXX note for tracker

[Michael Catanzaro <mcatanzaro src gnome org>]

commit 2a8804079e714f04a2258a253f9366a7ac4734ba
Author: Michael Catanzaro <mcatanzaro gnome org>
Date:   Fri Sep 4 11:14:52 2020 -0500

    Add XXX note for tracker

 help/C/developers.page | 1 +
 1 file changed, 1 insertion(+)
---
diff --git a/help/C/developers.page b/help/C/developers.page
index cff2b8cd..708cb993 100644
--- a/help/C/developers.page
+++ b/help/C/developers.page
@@ -71,6 +71,7 @@
     including the <code>SERVICE {}</code> statement, which allows one database
     to query from another.</p>
     <p>The tracker3 commandline tool has also seen many improvements.</p>
+    <p>XXX we still have tracker 2 as well. sthursfield to update this
   </section>
 
   <section id="gjs">