PHP/RestrictedPHPFunctions: rephrase error message

Follow up on the conversation about this phrasing in #2491 (comment) and #2693 (comment)

Also related to: WordPress/wpcs-docs#158

Author: jrfnl

WordPress/Sniffs/PHP/RestrictedPHPFunctionsSniff.php

@@ -35,7 +35,7 @@ public function getGroups() {
 		return array(
 			'create_function' => array(
 				'type'      => 'error',
-				'message'   => '%s() is deprecated as of PHP 7.2 and removed in PHP 8.0. Please use declared named or anonymous functions instead.',
+				'message'   => '%s() internally performs an eval(), which makes this a very dangerous function. For this reason, it was deprecated as of PHP 7.2 and removed in PHP 8.0. Please use anonymous functions, or declare a named function instead.',
 				'functions' => array(
 					'create_function',
 				),