Decrease fps_max_unfocused from 20 to 10

This used to be the default for android.
There's not much issues now with using a lower value, so a lower default on all platforms
is reasonable.
The only downside I know of is that if you re-focus the window, it can up till the
next client step until it goes back to normal fps, but 10 Hz feels fast enough.

builtin/settingtypes.txt

@@ -257,7 +257,7 @@ fps_max (Maximum FPS) int 60 1 4294967295
 vsync (VSync) bool false
 
 #    Maximum FPS when the window is not focused.
-fps_max_unfocused (FPS when unfocused) int 20 1 4294967295
+fps_max_unfocused (FPS when unfocused) int 10 1 4294967295
 
 #    View distance in nodes.
 viewing_range (Viewing range) int 190 20 4000

src/defaultsettings.cpp

@@ -243,7 +243,7 @@ void set_default_settings()
 	settings->setDefault("tooltip_show_delay", "400");
 	settings->setDefault("tooltip_append_itemname", "false");
 	settings->setDefault("fps_max", "60");
-	settings->setDefault("fps_max_unfocused", "20");
+	settings->setDefault("fps_max_unfocused", "10");
 	settings->setDefault("viewing_range", "190");
 	settings->setDefault("client_mesh_chunk", "1");
 	settings->setDefault("screen_w", "1024");