home: jujutsu: set 'home.diff-editor'

Otherwise it keeps nagging me with a hint to set it.

I'm not a big fan of this UI, I wish I add something closer to Git's
patch interface.

modules/home/jujutsu/default.nix

@@ -40,6 +40,11 @@ in
           lola = [ "lol" "-r" "all()" ];
         };
 
+        ui = {
+          # Stop nagging me about it, though I am not a fan of its UI.
+          diff-editor = ":builtin";
+        };
+
         templates = {
           # Equivalent to `commit.verbose = true` in Git
           draft_commit_description = "commit_description_verbose(self)";