zshrc: use dpkg-query instead of grep-status for debs-by-size alias

zshrc: use dpkg-query instead of grep-status for debs-by-size alias

Packages without Installed-Size cause a conflict for the
paste/sort command when using the grep-status command line.
So lets use dpkg-query with an according sed/sort command
line instead.

Thanks: Thorsten Glaser <tg@mirbsd.org>