Update outdated workstation packages

[eaon]

Workstation installs using the dev and staging environments currently result in an unusable client state due to outdated packages in the apt-test repo:

Package	apt	apt-test
securedrop-export	0.2.6	0.1.2
securedrop-proxy	0.3.1	0.1.5
securedrop-workstation-svs-disp	0.2.2	0.1.5

Scope of this issue is just to update those three to get the workstation dev environment working again, but a solution to update packages automatically to at least the most recent stable version would probably be a good idea