release-notes: mention removal of polipo module

Author: patka-123

nixos/doc/manual/release-notes/rl-2511.section.md

@@ -16,7 +16,7 @@
 
 <!-- To avoid merge conflicts, consider adding your item at an arbitrary place in the list instead. -->
 
-- Create the first release note entry in this section!
+- The `services.polipo` module has been removed as `polipo` is unmaintained and archived upstream.
 
 ## Other Notable Changes {#sec-release-25.11-notable-changes}