Drop Dental Record Manager (non-)package directory

According to the VDL page:

 http://www.va.gov/vdl/application.asp?appid=66

the "Dental Record Manager" is part of the "Dental" package and is not
its own package.  The parent commit already removed it from
Packages.csv.

Change-Id: I3eea1328b51f59e50211674fe405dc9219f6aca3