Add RSpec 4 compatibility (#17652)

* Remove outdated option

04078317ba

* Use the non-globally exposed RSpec syntax

https://github.com/rspec/rspec-core/pull/2803

* Use the non-globally exposed RSpec syntax, cont

https://github.com/rspec/rspec-core/pull/2803

* Comply to strict predicate matchers

See:
 - https://github.com/rspec/rspec-expectations/pull/1195
 - https://github.com/rspec/rspec-expectations/pull/1196
 - https://github.com/rspec/rspec-expectations/pull/1277

spec/lib/wizard/step_updater_spec.rb

@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-describe Wizard::StepUpdater do
+RSpec.describe Wizard::StepUpdater do
   before do
     SiteSetting.wizard_enabled = true
   end

spec/lib/wizard/wizard_builder_spec.rb

@@ -8,7 +8,7 @@ class GlobalPathInstance
   extend GlobalPath
 end
 
-describe Wizard::Builder do
+RSpec.describe Wizard::Builder do
   let(:moderator) { Fabricate.build(:moderator) }
   let(:wizard) { Wizard::Builder.new(moderator).build }
 

spec/lib/wizard/wizard_spec.rb

@@ -2,7 +2,7 @@
 
 require 'wizard'
 
-describe Wizard do
+RSpec.describe Wizard do
   fab!(:admin) { Fabricate(:admin) }
 
   before do

spec/lib/wizard/wizard_step_spec.rb

@@ -2,7 +2,7 @@
 
 require 'wizard'
 
-describe Wizard::Step do
+RSpec.describe Wizard::Step do
 
   let(:wizard) { Wizard.new(Fabricate.build(:user)) }
   let(:step) { wizard.create_step('test-step') }