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

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

priority-queue/src/test/java/com/iluwatar/priority/queue/PriorityMessageQueueTest.java

@@ -32,7 +32,7 @@ import org.junit.jupiter.api.Test;
 /**
  * Test case for order of messages
  */
-public class PriorityMessageQueueTest {
+class PriorityMessageQueueTest {
 
 
   @Test

priority-queue/src/test/java/com/iluwatar/priority/queue/QueueManagerTest.java

@@ -31,7 +31,7 @@ import org.junit.jupiter.api.Test;
 /**
  * Check queue manager
  */
-public class QueueManagerTest {
+class QueueManagerTest {
 
   @Test
   void publishMessage() {