Docs: Various docblock corrections.

See #53399


git-svn-id: https://develop.svn.wordpress.org/trunk@52299 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-admin/includes/image.php

@@ -687,8 +687,8 @@ function wp_exif_frac2dec( $str ) {
  *
  * @since 2.5.0
  *
- * @param string $str
- * @return int
+ * @param string $str A date string expected to be in Exif format (Y:m:d H:i:s).
+ * @return int|false The unix timestamp, or false on failure.
  */
 function wp_exif_date2ts( $str ) {
 	list( $date, $time ) = explode( ' ', trim( $str ) );