Remove unnecessary code (#4141)

src/main/java/com/thealgorithms/ciphers/Blowfish.java

@@ -1079,7 +1079,7 @@ public class Blowfish {
      */
     private String hexToBin(String hex) {
         String binary = "";
-        Long num;
+        long num;
         String binary4B;
         int n = hex.length();
         for (int i = 0; i < n; i++) {

src/main/java/com/thealgorithms/ciphers/HillCipher.java

@@ -160,7 +160,6 @@ public class HillCipher {
             System.out.println(
                 "Invalid key, as determinant = 0. Program Terminated"
             );
-            return;
         }
     }