Site Health: Only run the version checks on the main site.

The version checks that are setup in `wp-includes/update.php` do set up the action, but only for the main site.

Fixes #52135.

Props audrasjb, SergeyBiryukov, maxpertici, aaribaud.
 

Built from https://develop.svn.wordpress.org/trunk@50035


git-svn-id: http://core.svn.wordpress.org/trunk@49736 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-admin/includes/class-wp-site-health-auto-updates.php

@@ -90,7 +90,7 @@ class WP_Site_Health_Auto_Updates {
 	 * @return array The test results.
 	 */
 	public function test_wp_version_check_attached() {
-		if ( ! has_filter( 'wp_version_check', 'wp_version_check' ) ) {
+		if ( ( ! is_multisite() || ( is_main_site() && is_network_admin() ) ) && ! has_filter( 'wp_version_check', 'wp_version_check' ) ) {
 			return array(
 				'description' => sprintf(
 					/* translators: %s: Name of the filter used. */

wp-includes/version.php

@@ -13,7 +13,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '5.7-alpha-50034';
+$wp_version = '5.7-alpha-50035';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.