Site Health: Improve the error message displayed when activating a plugin that requires a higher version of PHP or WordPress.

This adds some extra details to the message:

* The current PHP or WordPress version.
* The plugin's minimum required PHP or WordPress version.
* A link to the support documentation on how to update PHP.

Props stuffradio, johnbillion, garrett-eclipse, sabernhardt, williampatton, SergeyBiryukov.
Fixes #48245.

git-svn-id: https://develop.svn.wordpress.org/trunk@48172 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-admin/update-core.php

@@ -88,6 +88,7 @@ function list_core_update( $update ) {
 			);
 
 			$annotation = wp_get_update_php_annotation();
+
 			if ( $annotation ) {
 				$php_update_message .= '</p><p><em>' . $annotation . '</em>';
 			}