Signs created in previous versions are not waxed by default

Signs from worlds that have been opened in versions before 23w12a get the is_waxed data value of 0b (false) when updated to 23w12a or higher. This makes the newly loaded signs' behavior inconsistent with how they worked in previous versions, since they can now be edited by being right-clicked.

Worlds that depend on signs not being editable would have to change every single sign block in the world to be waxed, which could mean a lot of effort if the world, for example, uses signs as decorations in large quantities.