Fix state update code

[PgBiel]

At get-page-dim-writer, calls to loc.position() - and thus the pos variables - must be made outside the state-name.update(...) call. Therefore, the pos variables must be declared above the .update lines seen below.

https://github.com/PgBiel/typst-tablex/blob/79c6bbd3914d7d72cece5e395c137c53f9973ec6/src/renderer/old.typ#L38-L58