refactoring: removed unused import in PasswordHasherTest

src/test/java/PasswordHasherTest.java

@@ -2,7 +2,6 @@ import org.junit.jupiter.api.Test;
 
 import static org.junit.Assert.assertThrows;
 import static org.junit.jupiter.api.Assertions.assertEquals;
-import static org.junit.jupiter.api.Assertions.assertNotNull;
 
 public class PasswordHasherTest {