Tests: Use a `@requires` annotation for `readonly()` function test.

The function is only defined by WordPress core on PHP < 8.1.

Follow-up to [51586].

See #59647.
Built from https://develop.svn.wordpress.org/trunk@57011


git-svn-id: http://core.svn.wordpress.org/trunk@56522 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/php-compat/readonly.php

@@ -4,7 +4,7 @@
  * to `wp_readonly()` in WordPress 5.9.0.
  *
  * In order to avoid PHP parser errors, this function was extracted
- * to this separate file and is only included conditionally on PHP 8.1.
+ * to this separate file and is only included conditionally on PHP < 8.1.
  *
  * Including this file on PHP >= 8.1 results in a fatal error.
  *

wp-includes/version.php

@@ -16,7 +16,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '6.5-alpha-57009';
+$wp_version = '6.5-alpha-57011';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.