PCE - Update patterns.c (#28)

Ultra-minor grammar suggestion as there are more than 1 screen in this option besides just White :)

240psuite/PCE/patterns.c

@@ -245,7 +245,7 @@ void RefreshTestPatterns()
 	drawmenutext(6, "Grids");
 	drawmenutext(7, "Monoscope");
 	drawmenutext(8, "Gray Ramp");
-	drawmenutext(9, "White & RGB Screen");
+	drawmenutext(9, "White & RGB Screens");
 	drawmenutext(10, "100 IRE");
 	drawmenutext(11, "Sharpness");
 	drawmenutext(12, "Overscan");