remove checkVizPackages

[aappling-usgs]

See USGS-VIZLAB/gage-conditions#40 (comment): we're trying out a Docker approach for vizzy development, and if that turns out to be as easy and useful as we anticipate, then we want to move package management from the vizlab package into vizzy-specific Dockerfiles.

David looked into this and determined that likey steps are:

1. Remove the checkVizPackages() call from vizmake()
2. Delete the definition of checkVizPackages() and any associated code that doesn't get used elsewhere.