fix: prune obselete test dependencies

[ryukyi]

Fixes #6579

Test plan

ran make test and all passed:

Checklist

This change accounts for:

• any required additional documentation
• any necessary AppArmor changes (added or removed application files)
• any impact on new SecureDrop installs and upgrades
• our dependency update policy

[ryukyi]

I was able to docker build after pruning test deps. I was unsure how of command/s to run tests. May I please get some help? I'll also update docs to include this in contributing.

Ok make test to running tests but takes many hours for me to run on x7 thinkpad