Multisite: Only query for one site in domain_exists().

`get_sites()` queries for a maximum of 100 records by default. In `domain_exists()`, we only use one.

Props danieltj, spacedmonkey.
Fixes #42072.


git-svn-id: https://develop.svn.wordpress.org/trunk@41736 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-includes/ms-functions.php

@@ -342,6 +342,7 @@ function get_blog_id_from_url( $domain, $path = '/' ) {
 		'domain' => $domain,
 		'path' => $path,
 		'fields' => 'ids',
+		'number' => 1,
 	);
 	$result = get_sites( $args );
 	$id = array_shift( $result );