Docs: Clarify return value for wp_get_default_extension_for_mime_type().

Follow-up to [51653].

Props rollybueno, SergeyBiryukov.
See #63166.

git-svn-id: https://develop.svn.wordpress.org/trunk@60696 602fd350-edb4-49c9-b593-d223f7449a82

Author: SergeyBiryukov

src/wp-includes/functions.php

@@ -3007,14 +3007,13 @@ function wp_ext2type( $ext ) {
 }
 
 /**
- * Returns first matched extension for the mime-type,
- * as mapped from wp_get_mime_types().
+ * Returns the first matched extension for the mime type, as mapped from wp_get_mime_types().
  *
  * @since 5.8.1
  *
- * @param string $mime_type
- *
- * @return string|false
+ * @param string $mime_type The mime type to search.
+ * @return string|false The first matching file extension, or false if no extensions are found
+ *                      for the given mime type.
  */
 function wp_get_default_extension_for_mime_type( $mime_type ) {
 	$extensions = explode( '|', array_search( $mime_type, wp_get_mime_types(), true ) );