Fix palindrome unit test

One of the test cases was not as described in the test method name. Also corrected formatting in another test case.

testing-modules/testing-libraries/src/test/java/com/baeldung/mutation/PalindromeUnitTest.java

@@ -11,7 +11,7 @@ public class PalindromeUnitTest {
     @Test
     public void whenEmptyString_thanAccept() {
         Palindrome palindromeTester = new Palindrome();
-        assertTrue(palindromeTester.isPalindrome("noon"));
+        assertTrue(palindromeTester.isPalindrome(""));
     }
 
     @Test