Fixed typo

src/main/java/GradientDescent.java

@@ -21,7 +21,7 @@ public class GradientDescent {
 
     /**
      * Performs gradient descent on a function f: ℝ -> ℝ
-     * @param f vector-valued function
+     * @param f real-valued function
      * @param initialX initial X vector
      * @param maxIterations maximum number of iterations
      * @return approximation of the nearest local minimum