Remove unnecessary blank line in ComplexNumberMultiplication

Author: muskansngh07

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

@@ -45,5 +45,4 @@ public static String complexNumberMultiply(String num1, String num2) {
 
         return real + "+" + imag + "i";
     }
-
 }