Only apply sprite_zoom_min setting when suitable zoom levels are available

Only discard sprite zoom levels when a suitable higher zoom level is
defined in the same colour mode

See: https://github.com/OpenTTD/OpenTTD/issues/9804

src/settings.cpp

@@ -1787,19 +1787,6 @@ static bool LinkGraphDistributionSettingGUI(SettingOnGuiCtrlData &data)
 	}
 }
 
-static bool SpriteZoomMinSettingGUI(SettingOnGuiCtrlData &data)
-{
-	switch (data.type) {
-		case SOGCT_DESCRIPTION_TEXT:
-			SetDParam(0, data.text);
-			data.text = STR_CONFIG_SETTING_SPRITE_ZOOM_MIN_HELPTEXT_EXTRA;
-			return true;
-
-		default:
-			return false;
-	}
-}
-
 static bool AllowRoadStopsUnderBridgesSettingGUI(SettingOnGuiCtrlData &data)
 {
 	switch (data.type) {