Docs: Correct the type of the $cache parameter in embed_oembed_html.

The value cannot be `false` at this point, as the filter is only applied to non-empty output.

Follow-up to [25726], [46661].

Props apermo, xate.
Fixes #63220.

git-svn-id: https://develop.svn.wordpress.org/trunk@60127 602fd350-edb4-49c9-b593-d223f7449a82

Author: SergeyBiryukov

src/wp-includes/class-wp-embed.php

@@ -283,10 +283,10 @@ public function shortcode( $attr, $url = '' ) {
 				 *
 				 * @see WP_Embed::shortcode()
 				 *
-				 * @param string|false $cache   The cached HTML result, stored in post meta.
-				 * @param string       $url     The attempted embed URL.
-				 * @param array        $attr    An array of shortcode attributes.
-				 * @param int          $post_id Post ID.
+				 * @param string $cache   The cached HTML result, stored in post meta.
+				 * @param string $url     The attempted embed URL.
+				 * @param array  $attr    An array of shortcode attributes.
+				 * @param int    $post_id Post ID.
 				 */
 				return apply_filters( 'embed_oembed_html', $cache, $url, $attr, $post_id );
 			}