zsh: 5.6.1 -> 5.6.2

From upstream's NEWS:

> Changes from 5.6.1 to 5.6.2
> ---------------------------
>
> Fix another SIGTTOU case.
>
> Fix SIGWINCH being ignored when zsh is not in the foreground.
>
> The release tarballs are now compressed using xz(1), whereas previously
> both xz(1) and gzip(1) versions were available.  If this gets in your way,
> give us a shout.
>