X11: Fix attribs not applied on leaving fullscreen

If the GLFW_DECORATED and/or GLFW_FLOATING window attributes were
changed while in fullscreen mode, the changes did not take effect when
the window entered windowed mode.

Bug reported on the GLFW forum.
https://discourse.glfw.org/t/turning-on-off-window-decorations-while-in-full-screen-wont-work-properly/1780

src/x11_window.c

@@ -2485,7 +2485,11 @@ void _glfwPlatformSetWindowMonitor(_GLFWwindow* window,
     }
 
     if (window->monitor)
+    {
+        _glfwPlatformSetWindowDecorated(window, window->decorated);
+        _glfwPlatformSetWindowFloating(window, window->floating);
         releaseMonitor(window);
+    }
 
     _glfwInputWindowMonitor(window, monitor);
     updateNormalHints(window, width, height);