docs: update config sample code

Author: kenjis

user_guide_src/source/libraries/validation/003.php

@@ -4,7 +4,9 @@
 
 class Validation
 {
-    public $ruleSets = [
+    // ...
+
+    public array $ruleSets = [
         \CodeIgniter\Validation\CreditCardRules::class,
         \CodeIgniter\Validation\FileRules::class,
         \CodeIgniter\Validation\FormatRules::class,

user_guide_src/source/libraries/validation/033.php

@@ -9,7 +9,9 @@
 
 class Validation
 {
-    public $ruleSets = [
+    // ...
+
+    public array $ruleSets = [
         Rules::class,
         FormatRules::class,
         FileRules::class,