Use gemfile.d for upstream CI (#116)

The gemspec shouldn't contain environment variables, because it's also
used in other contexts where it could break.

In common CI we read gemfile.d/*.rb so this is the best place for
bundler overrides.

Fixes: 3eedb81 ("feat(actions): switch to upstream CI templates (#113)")

foreman_wreckingball.gemspec

@@ -19,13 +19,7 @@ Gem::Specification.new do |s|
   s.test_files = Dir['test/**/*']
 
   s.add_dependency 'foreman_puppet'
-
-  case ENV['FOREMAN_VERSION']
-  when '3.7-stable', '3.8-stable'
-    s.add_dependency 'foreman-tasks', '>= 8.0.0', '< 9.0.0'
-  else
-    s.add_dependency 'foreman-tasks'
-  end
+  s.add_dependency 'foreman-tasks'
 
   s.add_development_dependency 'rdoc'
   s.add_development_dependency 'theforeman-rubocop', '~> 0.1.2'

gemfile.d/tasks.rb

@@ -0,0 +1,6 @@
+# frozen_string_literal: true
+
+case ENV['FOREMAN_VERSION']
+when '3.7-stable', '3.8-stable'
+  gem 'foreman-tasks', '~> 8.0'
+end