Fix #2840, now Invisible and Speed 2d icon powerups are visible when aren't available to pick up

scripts/relics.shader

@@ -89,7 +89,7 @@ models/relics/sign_invisible
 	nopicmip
 	{
 		map models/relics/sign_invisible
-		blendfunc add
+		blendfunc blend
 	}
 }
 
@@ -144,7 +144,7 @@ models/relics/sign_speed
 	nopicmip
 	{
 		map models/relics/sign_speed
-		blendfunc add
+		blendfunc blend
 	}
 }