Add additional assertions to StochasticMatrixTest

Author: Dsannue

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

@@ -1,6 +1,10 @@
 package com.thealgorithms.matrix;
 
-import static org.junit.jupiter.api.Assertions.*;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+import static org.junit.jupiter.api.Assertions.assertFalse;
+
+import static org.junit.jupiter.api.Assertions.assertThrows;
 
 import org.junit.jupiter.api.Test;