docs: remove @todo

GET/POST data and the Validation errors are used together when the validation errors occur.
So that withInput() also save the validation errors is not bad.

system/HTTP/RedirectResponse.php

@@ -79,8 +79,8 @@ public function back(?int $code = null, string $method = 'auto')
     }
 
     /**
-     * Specifies that the current $_GET and $_POST arrays should be
-     * packaged up with the response.
+     * Sets the current $_GET and $_POST arrays in the session.
+     * This also saves the validation errors.
      *
      * It will then be available via the 'old()' helper function.
      *
@@ -94,22 +94,18 @@ public function withInput()
             'post' => $_POST ?? [],
         ]);
 
-        // @TODO Remove this in the future.
-        //      See https://github.com/codeigniter4/CodeIgniter4/issues/5839#issuecomment-1086624600
         $this->withErrors();
 
         return $this;
     }
 
     /**
-     * Set validation errors in the session.
+     * Sets validation errors in the session.
      *
      * If the validation has any errors, transmit those back
      * so they can be displayed when the validation is handled
      * within a method different than displaying the form.
      *
-     * @TODO Make this method public when removing $this->withErrors() in withInput().
-     *
      * @return $this
      */
     private function withErrors(): self