Fix breakage of the old Lua API due to recent changes

Specifically, the CPos::CenterPosition -> Map::CenterOfCell rename (#5758),
as well as the additional argument to Paradrop::SetLZ (#5695).

mods/common/lua/map.lua

@@ -70,6 +70,10 @@ Map.ExpandFootprint = function(cells, allowDiagonal)
 	return Utils.EnumerableToTable(Internal.ExpandFootprint(cells, allowDiagonal))
 end
 
+Map.CenterOfCell = function(position)
+	return Internal.CenterOfCell(position)
+end
+
 CPos.New = function(x, y)
 	return OpenRA.New("CPos", { { x, "Int32" }, { y, "Int32" } })
 end
@@ -102,4 +106,4 @@ end
 
 WRange.FromCells = function(cells)
 	return WRange.New(cells * 1024)
-end
+end