chore(spp_farmer_registry_dashboard): drop tests/ — blocked by missing spp_dashboard_base in OpenSPP2

The dashboard module depends on spp_dashboard_base, which still lives in
the private openspp-modules-v2 repo and isn't mounted in the OpenSPP2 CI
runner. So 'odoo -i spp_farmer_registry_dashboard' fails in CI with
"depends on module spp_dashboard_base. But the latter module is not
available".

Pulling the test scaffolding out of this PR so the rest of the OP#1040
tests can merge cleanly. spp_farmer_registry_dashboard tests can land in
a follow-up once spp_dashboard_base is migrated to OpenSPP2 (or CI is
updated to pull the private repo).

Author: emjay0921