Docs: Correct a comment about WebP constants in `wp-includes/compat.php`.

Follow-up to [50810], [50814].

Props GaryJ, rtm909.
Fixes #53680.
Built from https://develop.svn.wordpress.org/trunk@51474


git-svn-id: http://core.svn.wordpress.org/trunk@51085 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/compat.php

@@ -371,10 +371,12 @@ if ( ! function_exists( 'is_iterable' ) ) {
 	}
 }
 
-// WebP constants are only defined in PHP 7.1+.
+// IMAGETYPE_WEBP constant is only defined in PHP 7.1 or later.
 if ( ! defined( 'IMAGETYPE_WEBP' ) ) {
 	define( 'IMAGETYPE_WEBP', 18 );
 }
+
+// IMG_WEBP constant is only defined in PHP 7.0.10 or later.
 if ( ! defined( 'IMG_WEBP' ) ) {
 	define( 'IMG_WEBP', IMAGETYPE_WEBP ); // phpcs:ignore PHPCompatibility.Constants.NewConstants.imagetype_webpFound
 }

wp-includes/version.php

@@ -13,7 +13,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '5.9-alpha-51473';
+$wp_version = '5.9-alpha-51474';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.