General: Rename the `wp_error_checked` action to `is_wp_error_instance` for clarity.

Follow-up to [49022], [49023].

Props johnbillion, helen, johnjamesjacoby, Mte90, alexstandiford, hellofromTonya, jnylen0, SergeyBiryukov.
Fixes #40568.
Built from https://develop.svn.wordpress.org/trunk@49635


git-svn-id: http://core.svn.wordpress.org/trunk@49373 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/load.php

@@ -1505,13 +1505,13 @@ function is_wp_error( $thing ) {
 
 	if ( $is_wp_error ) {
 		/**
-		 * Fires when `is_wp_error()` is called and it's an instance of `WP_Error`.
+		 * Fires when `is_wp_error()` is called and its parameter is an instance of `WP_Error`.
 		 *
 		 * @since 5.6.0
 		 *
 		 * @param WP_Error $thing The error object passed to `is_wp_error()`.
 		 */
-		do_action( 'wp_error_checked', $thing );
+		do_action( 'is_wp_error_instance', $thing );
 	}
 
 	return $is_wp_error;

wp-includes/version.php

@@ -13,7 +13,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '5.6-beta4-49634';
+$wp_version = '5.6-beta4-49635';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.