refactor: remove code smell java:S5786 (#2159)

https://sonarcloud.io/organizations/iluwatar/rules?open=java%3AS5786&rule_key=java%3AS5786

guarded-suspension/src/test/java/com/iluwatar/guarded/suspension/GuardedQueueTest.java

@@ -33,7 +33,7 @@ import org.junit.jupiter.api.Test;
 /**
  * Test for Guarded Queue
  */
-public class GuardedQueueTest {
+class GuardedQueueTest {
   private volatile Integer value;
 
   @Test