Incompatible with older packrat

[rstub]

According to the DESCRIPTION it should be possible to use current rsconnect together with packrat 0.4.8-1. However, using this combination for a deployment with a non CRAN package leads to the error

Error: Unable to retrieve package records for the following packages:

• 'non_CRAN_package'

This goes away when packrat is updated to the most recent version. See internal support ticket 48697.

[jmcphers]

@kevinushey Do you know the true Packrat version on which we depend? (should be as simple as updating DESCRIPTION)

[kevinushey]

I think we can just depend on Packrat 0.5.0 -- that version is now already a couple years old, and appears to be new enough to resolve that user's issue.