Docs: The $feedname parameter in add_feed() should not start with an underscore.

Props snehapatil02, hellofromtonya, narenin.
Fixes #59945.


git-svn-id: https://develop.svn.wordpress.org/trunk@59059 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-includes/rewrite.php

@@ -244,7 +244,7 @@ function remove_permastruct( $name ) {
  *
  * @global WP_Rewrite $wp_rewrite WordPress rewrite component.
  *
- * @param string   $feedname Feed name.
+ * @param string   $feedname Feed name. Should not start with '_'.
  * @param callable $callback Callback to run on feed display.
  * @return string Feed action name.
  */