Rein in light spread by correcting falloff value

* Fixes #5018

src/BlockInfo.cpp

@@ -684,32 +684,8 @@ NIBBLETYPE cBlockInfo::GetSpreadLightFalloff(const BLOCKTYPE Block)
 		case E_BLOCK_STATIONARY_WATER:
 		case E_BLOCK_WATER: return 3;
 
-		// Light does not pass through these blocks at all:
-		case E_BLOCK_ACACIA_WOOD_STAIRS:
-		case E_BLOCK_BIRCH_WOOD_STAIRS:
-		case E_BLOCK_BRICK_STAIRS:
-		case E_BLOCK_COBBLESTONE_STAIRS:
-		case E_BLOCK_DARK_OAK_WOOD_STAIRS:
-		case E_BLOCK_DOUBLE_RED_SANDSTONE_SLAB:
-		case E_BLOCK_DOUBLE_STONE_SLAB:
-		case E_BLOCK_DOUBLE_WOODEN_SLAB:
-		case E_BLOCK_FARMLAND:
-		case E_BLOCK_JUNGLE_WOOD_STAIRS:
-		case E_BLOCK_NETHER_BRICK_STAIRS:
-		case E_BLOCK_OAK_WOOD_STAIRS:
-		case E_BLOCK_PURPUR_DOUBLE_SLAB:
-		case E_BLOCK_PURPUR_SLAB:
-		case E_BLOCK_PURPUR_STAIRS:
-		case E_BLOCK_QUARTZ_STAIRS:
-		case E_BLOCK_RED_SANDSTONE_SLAB:
-		case E_BLOCK_RED_SANDSTONE_STAIRS:
-		case E_BLOCK_SANDSTONE_STAIRS:
-		case E_BLOCK_SPRUCE_WOOD_STAIRS:
-		case E_BLOCK_STONE_BRICK_STAIRS:
-		case E_BLOCK_STONE_SLAB:
-		case E_BLOCK_WOODEN_SLAB: return 15;
-
-		default: return 0;
+		// Light does not pass through anything else (note: including tilled farmland, stairs, and slabs):
+		default: return 15;
 	}
 }