NamingConventions/PrefixAllGlobals: modify test to include class constant type

This commit modifies one of the existing class constants in the code used in the `WordPress.NamingConventions.PrefixAllGlobal` tests to have a type. This is just to ensure that there is a test for typed class constants added in PHP 8.3 as this sniff listens to the `T_CONST` token.

The sniff was already handling typed class constants correctly and no change to the sniff code is needed.

Author: rodrigoprimo

WordPress/Tests/NamingConventions/PrefixAllGlobalsUnitTest.1.inc

@@ -276,7 +276,7 @@ apply_filters( $_REQUEST['else'] ); // Warning.
 
 class Acronym_Dynamic_Hooks {
 	const FILTER = 'acronym';
-	const FILTER_WITH_UNDERSCORE = 'acronym_';
+	const ?string FILTER_WITH_UNDERSCORE = 'acronym_';
 
 	protected $filter = 'acronym';
 	protected $filter_with_underscore = 'acronym_';