Update flake.nix for 1.2.1

Author: firecat53

flake.nix

@@ -27,7 +27,7 @@
           default = self.packages.${system}.pangolin-newt;
           pangolin-newt = pkgs.buildGoModule {
             pname = "pangolin-newt";
-            version = "1.2.0";
+            version = "1.2.1";
 
             src = ./.;