python310Packages.gcovr: add changelog to meta

pkgs/development/python-modules/gcovr/default.nix

···
   meta = with lib; {
     description = "Python script for summarizing gcov data";
     homepage = "https://www.gcovr.com/";
+    changelog = "https://github.com/gcovr/gcovr/blob/${version}/CHANGELOG.rst";
     license = licenses.bsd0;
     maintainers = with maintainers; [ ];
   };