Define nullable parameter types explicitly

Not doing so will become deprecated in PHP 8.4

Author: W0rma

src/Codeception/Module/REST.php

@@ -1330,7 +1330,7 @@ public function dontSeeResponseContainsJson(array $json = []): void
      * @part json
      * @see JsonType
      */
-    public function seeResponseMatchesJsonType(array $jsonType, string $jsonPath = null): void
+    public function seeResponseMatchesJsonType(array $jsonType, ?string $jsonPath = null): void
     {
         $jsonArray = new JsonArray($this->connectionModule->_getResponseContent());
         if ($jsonPath) {
@@ -1347,7 +1347,7 @@ public function seeResponseMatchesJsonType(array $jsonType, string $jsonPath = n
      * @param array $jsonType JsonType structure
      * @see seeResponseMatchesJsonType
      */
-    public function dontSeeResponseMatchesJsonType(array $jsonType, string $jsonPath = null): void
+    public function dontSeeResponseMatchesJsonType(array $jsonType, ?string $jsonPath = null): void
     {
         $jsonArray = new JsonArray($this->connectionModule->_getResponseContent());
         if ($jsonPath) {

src/Codeception/Step/AsJson.php

@@ -7,7 +7,7 @@
 
 class AsJson extends Action implements GeneratedStep
 {
-    public function run(ModuleContainer $container = null)
+    public function run(?ModuleContainer $container = null)
     {
         $container->getModule('REST')->haveHttpHeader('Content-Type', 'application/json');
         $resp = parent::run($container);