The previous version of the script did not quote VAGRANTUSERNAME, which caused
an error when running the script if the username contained `-` or other characters
that affect the Postgres syntax. Fix this using double-quotes.
This was only necessary for PGroonga 1.x, and the `pgroonga` schema
will most likely be removed at some point inthe future, which will
make this statement error out.
Drop the unnecessary statement.
