docs: improve lockable object

lockable-object/src/test/java/com/iluwatar/lockableobject/CreatureTest.java

@@ -90,7 +90,7 @@ class CreatureTest {
     Assertions.assertEquals(orc, sword.getLocker());
   }
 
-  void killCreature(Creature source, Creature target) throws InterruptedException {
+  void killCreature(Creature source, Creature target) {
     while (target.isAlive()) {
       source.attack(target);
     }

lockable-object/src/test/java/com/iluwatar/lockableobject/ExceptionsTest.java

@@ -29,17 +29,17 @@ import org.junit.jupiter.api.Test;
 
 class ExceptionsTest {
 
-  private String msg = "test";
+  private static final String MSG = "test";
 
   @Test
   void testException(){
     Exception e;
     try{
-      throw new LockingException(msg);
+      throw new LockingException(MSG);
     }
     catch(LockingException ex){
       e = ex;
     }
-    Assertions.assertEquals(msg, e.getMessage());
+    Assertions.assertEquals(MSG, e.getMessage());
   }
 }