Docs: Correct documentation for the `$meta_key` parameter of `get_metadata_default()`.

The parameter is required, not optional.

Follow-up to [48502].

See #43941.
Built from https://develop.svn.wordpress.org/trunk@48504


git-svn-id: http://core.svn.wordpress.org/trunk@48266 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/meta.php

@@ -596,8 +596,7 @@ function get_metadata_raw( $meta_type, $object_id, $meta_key = '', $single = fal
  * @param string $meta_type Type of object metadata is for. Accepts 'post', 'comment', 'term', 'user',
  *                          or any other object type with an associated meta table.
  * @param int    $object_id ID of the object metadata is for.
- * @param string $meta_key  Metadata key. If not specified, retrieve all metadata for
- *                          the specified object. Default empty.
+ * @param string $meta_key  Metadata key.
  * @param bool   $single    Optional. If true, return only the first value of the specified meta_key.
  *                          This parameter has no effect if meta_key is not specified. Default false.
  * @return mixed Single metadata value, or array of values.

wp-includes/version.php

@@ -13,7 +13,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '5.5-beta2-48503';
+$wp_version = '5.5-beta2-48504';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.