Fix checkstyle issues.

Author: the-yash-rajput

src/main/java/com/thealgorithms/physics/GroundToGroundProjectileMotion.java

@@ -8,7 +8,7 @@
  *
  * @author [Yash Rajput](https://github.com/the-yash-rajput)
  */
-public class GroundToGroundProjectileMotion {
+public final class GroundToGroundProjectileMotion {
 
     private GroundToGroundProjectileMotion() {
         throw new AssertionError("No instances.");