Code cleanup (#4246)

src/main/java/com/thealgorithms/strings/LongestPalindromicSubstring.java

@@ -12,6 +12,7 @@ class LongestPalindromicSubstring {
         System.out.print("Enter the string: ");
         str = sc.nextLine();
         System.out.println("Longest substring is : " + s.longestPalindrome(str));
+        sc.close();
     }
 }
 

src/main/java/com/thealgorithms/strings/WordLadder.java

@@ -1,6 +1,5 @@
 package com.thealgorithms.strings;
 
-import java.util.Arrays;
 import java.util.HashSet;
 import java.util.LinkedList;
 import java.util.List;