chore: final formatting and test fix for BigInteger

Author: VanshSharma3

src/test/java/com/thealgorithms/maths/FactorialTest.java

@@ -2,6 +2,7 @@
 
 import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.junit.jupiter.api.Assertions.assertThrows;
+
 import java.math.BigInteger;
 import org.junit.jupiter.api.Test;