General: Cast $public param to bool in do_robots().

This changeset properly casts the `$public` variable into `bool` in `do_robots()` for better consistency between code and docs.

Props SergeyBiryukov, shailu25, kapilpaul.
Fixes #63039.



git-svn-id: https://develop.svn.wordpress.org/trunk@59946 602fd350-edb4-49c9-b593-d223f7449a82

Author: audrasjb

src/wp-includes/functions.php

@@ -1715,7 +1715,7 @@ function do_robots() {
 	do_action( 'do_robotstxt' );
 
 	$output = "User-agent: *\n";
-	$public = get_option( 'blog_public' );
+	$public = (bool) get_option( 'blog_public' );
 
 	$site_url = parse_url( site_url() );
 	$path     = ( ! empty( $site_url['path'] ) ) ? $site_url['path'] : '';