maintainers: drop abbradar

Listed as maintainer for ~170 packages but last commit that made it to
master was 6786ceb in February 2022.

Unresponsive on PRs, such as i.e. #411522

pkgs/development/python2-modules/scandir/default.nix

@@ -25,6 +25,6 @@ buildPythonPackage rec {
     description = "Better directory iterator and faster os.walk()";
     homepage = "https://github.com/benhoyt/scandir";
     license = licenses.gpl3;
-    maintainers = with maintainers; [ abbradar ];
+    maintainers = [ ];
   };
 }