[QA] "securedrop-admin verify" does not support force arg

[conorsch]

Description

Running ./securedrop-admin verify on release/2.1.0 fails, because there's no prod-signed tag on that commit.

Steps to Reproduce

1. Check out release/2.1.0 in Tails, configured VMs
2. Run ./securedrop-admin verify, observe error message and friendly recommendation to try the "--force" flag
3. Run ./securedrop-admin --force verify as recommended, observe error message about flag not being understood

Expected Behavior

./securedrop-admin --force verify skips tag verification logic, just like ./securedrop-admin --force install does.

Actual Behavior

./securedrop-admin --force verify does not recognize the --force flag at all.

[zenmonkeykstop]

IMO verify shouldn't do the version check at all - it doesn't run any playbook that can change the workstation or server state, so it doesn't matter which version you're on locally (altho the onus is then on the user to make sure they're using the version they expect).