godu: don't pin to go1.16

pkgs/top-level/all-packages.nix

···
 
   gorilla-bin = callPackage ../tools/security/gorilla-bin { };
 
-  godu = callPackage ../tools/misc/godu {
-    buildGoModule = buildGo116Module;
-  };
+  godu = callPackage ../tools/misc/godu { };
 
   goss = callPackage ../tools/misc/goss { };