This is pretty simple:
glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 4); // Major = 4
glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3); // Major was 4, now it is 3.
// Minor = ??? [Something < 2]
You need to use glfwWindowHint (GLFW_CONTEXT_VERSION_MINOR, 3);
instead for the second hint.