Use exact version for rubocop-pacakaging
Use exact version for rubocop-pacakaging

The current criteria is to use `~> x.y` for gems
that have reached 1.0, and an exact version for
gem still in the 0.x phase.

Co-authored-by: David Rodríguez <96558bf9378c437d3852fad4fa4b4bd63aeb6eda@riseup.net>

activeadmin/activeadmin,deivid-rodriguez/activeadmin,deivid-rodriguez/activeadmin,javierjulio/activeadmin,activeadmin/activeadmin,javierjulio/activeadmin,javierjulio/activeadmin,deivid-rodriguez/activeadmin,activeadmin/activeadmin