Add explicit deprecation notices for mongo-express and teamspeak (#2656)

All supported tags of these were removed in https://github.com/docker-library/official-images/commit/f92e06ed2ca17b53991ae04fb61ede874e3965db (so they've both said "No supported tags" since Jun 4, 2025).

mongo-express/README-short.txt

@@ -1 +1 @@
-Web-based MongoDB admin interface, written with Node.js and express
+DEPRECATED; Web-based MongoDB admin interface, written with Node.js and express

mongo-express/deprecated.md

@@ -0,0 +1 @@
+This image is deprecated due to maintainer inactivity (last updated Apr 2024; [docker-library/official-images#16597](https://github.com/docker-library/official-images/pull/16597)).

teamspeak/README-short.txt

@@ -1 +1 @@
-TeamSpeak is software for quality voice communication via the Internet.
+DEPRECATED; TeamSpeak is software for quality voice communication via the Internet.

teamspeak/deprecated.md

@@ -0,0 +1 @@
+This image is deprecated due to maintainer inactivity (last updated Sep 2023; [docker-library/official-images#15332](https://github.com/docker-library/official-images/pull/15332)).