Fix bug while releasing session key:

Uncaught exception 'Meritoo\LimeSurvey\ApiClient\Exception\UnknownMethodException' with message 'The 'get_session_key' type of name of method used while talking to the LimeSurvey's API is unknown

tests/Meritoo/LimeSurvey/Test/ApiClient/Type/MethodTypeTest.php

@@ -12,6 +12,7 @@ use Generator;
 use Meritoo\Common\Test\Base\BaseTypeTestCase;
 use Meritoo\LimeSurvey\ApiClient\Exception\UnknownMethodException;
 use Meritoo\LimeSurvey\ApiClient\Type\MethodType;
+use Meritoo\LimeSurvey\ApiClient\Type\SystemMethodType;
 
 /**
  * Test case of the type of method used while talking with LimeSurvey's API
@@ -88,6 +89,14 @@ class MethodTypeTest extends BaseTypeTestCase
         yield[
             MethodType::LIST_SURVEYS,
         ];
+
+        yield[
+            SystemMethodType::GET_SESSION_KEY,
+        ];
+
+        yield[
+            SystemMethodType::RELEASE_SESSION_KEY,
+        ];
     }
 
     /**