UI: Fix label offset on projector view

Labels on 18-scene multiview were skewed. This commit adjusted the
location of the labels.

UI/window-projector.cpp

@@ -191,11 +191,8 @@ static inline uint32_t labelOffset(obs_source_t *label, uint32_t cx)
 {
 	uint32_t w = obs_source_get_width(label);
 
-	int n; // Number of scenes per row
+	int n; // Twice of scale factor of preview and program scenes
 	switch (multiviewLayout) {
-	case MultiviewLayout::HORIZONTAL_TOP_18_SCENES:
-		n = 6;
-		break;
 	case MultiviewLayout::HORIZONTAL_TOP_24_SCENES:
 		n = 6;
 		break;