Remove dependency versions from requirements-dev.in
Remove dependency versions from requirements-dev.in

There is no need to specify versions in this file, requirements-dev.txt
and pip-compile lock the versions for us.

alphagov/digitalmarketplace-supplier-frontend,alphagov/digitalmarketplace-supplier-frontend,alphagov/digitalmarketplace-supplier-frontend,alphagov/digitalmarketplace-supplier-frontend