Real-time collaboration: Remove ghost awareness state explicitly when refreshing.

Syncs PHP changes from WordPress/gutenberg#75883. Changes the real-time collaboration polling server endpoint to accept null for awareness values, which is used to explicitly disconnect users leaving the page and remove their awareness data more quickly.

CI run: WordPress/wordpress-develop#11049.

Fixes #64622.
Props alecgeatches.
Built from https://develop.svn.wordpress.org/trunk@61746


git-svn-id: http://core.svn.wordpress.org/trunk@61052 1a063a9b-81f0-0310-95a4-ce76da25c4cd

Author: ellatrix

wp-includes/collaboration/class-wp-http-polling-sync-server.php

@@ -122,7 +122,7 @@ public function register_routes(): void {
 			),
 			'awareness' => array(
 				'required' => true,
-				'type'     => 'object',
+				'type'     => array( 'object', 'null' ),
 			),
 			'client_id' => array(
 				'minimum'  => 1,

wp-includes/version.php

@@ -16,7 +16,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '7.0-beta1-61745';
+$wp_version = '7.0-beta1-61746';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.