Silence Mocha warnings

Deprecation warnings are incorrect because there is a misunderstanding
around the Ruby keyword arguments change in 3.0.

Ref: freerange/mocha#593

Close activeadmin#876

test/test_helper.rb

@@ -26,6 +26,10 @@
 require "active_model"
 require "action_controller"
 
+# TODO: Remove warning gem and the following lines when freerange/mocha#593 will be fixed
+require "warning"
+Warning.ignore(/Mocha deprecation warning .+ expected keyword arguments .+ but received positional hash/)
+
 require 'rails-controller-testing'
 Rails::Controller::Testing.install