Fix removing vars from variables_to_prompt

inni/cli.py

@@ -62,7 +62,7 @@ def _login_out(ctx: click.Context, login: bool):
         variables_to_prompt.update(
             module.template_variables()["login" if login else "logout"]
         )
-    variables_to_prompt.remove("vars")
+    variables_to_prompt -= {"vars"}
 
     responses: dict[str, Any] = {
         "vars": ctx.obj.get("vars", {}),