Add import statement for JUnit in StochasticMatrixTest

Author: Dsannue

src/test/java/com/thealgorithms/matrix/StochasticMatrixTest.java

@@ -1,6 +1,7 @@
 package com.thealgorithms.matrix;
 
 import static org.junit.jupiter.api.Assertions.*;
+
 import org.junit.jupiter.api.Test;
 
 class StochasticMatrixTest {