Fixed video mode being set to the current mode

There is no need in switching to the same video mode.
For example, it happens in this case:

```C
GLFWmonitor *primary_monitor = glfwGetPrimaryMonitor();
const GLFWvidmode *video_mode = glfwGetVideoMode(primary_monitor);
GLFWwindow *window = glfwCreateWindow(video_mode->width, video_mode->height,
                                      title, primary_monitor, NULL);
```