Disable resizable window

You should enable it in order to make it the right size with i3wm, but
for common window managers, you have to let it disabled.

godot/project.godot

@@ -35,6 +35,7 @@ config/icon="res://icon.png"
 
 window/size/width=400
 window/size/height=400
+window/size/resizable=false
 window/size/test_width=400
 window/size/test_height=400
 window/handheld/orientation="portrait"