Upgrade RSpec to 4.0.0 from 4.0.0.beta4

The stable version is now released

Gemfile

@@ -355,7 +355,7 @@ group :development, :test do
 
   gem 'database_cleaner', '~> 1.7.0'
   gem 'factory_bot_rails', '~> 5.1.0'
-  gem 'rspec-rails', '~> 4.0.0.beta4'
+  gem 'rspec-rails', '~> 4.0.0'
 
   # Prevent occasions where minitest is not bundled in packaged versions of ruby (see #3826)
   gem 'minitest', '~> 5.11.0'

Gemfile.lock

@@ -614,7 +614,7 @@ GEM
       activesupport (>= 4)
       railties (>= 4)
       request_store (~> 1.0)
-    loofah (2.4.0)
+    loofah (2.5.0)
       crass (~> 1.0.2)
       nokogiri (>= 1.5.9)
     lru_redux (1.1.0)
@@ -906,7 +906,7 @@ GEM
       rspec-mocks (~> 3.9.0)
     rspec-core (3.9.1)
       rspec-support (~> 3.9.1)
-    rspec-expectations (3.9.0)
+    rspec-expectations (3.9.1)
       diff-lcs (>= 1.2.0, < 2.0)
       rspec-support (~> 3.9.0)
     rspec-mocks (3.9.1)
@@ -918,7 +918,7 @@ GEM
       proc_to_ast
       rspec (>= 2.13, < 4)
       unparser
-    rspec-rails (4.0.0.beta4)
+    rspec-rails (4.0.0)
       actionpack (>= 4.2)
       activesupport (>= 4.2)
       railties (>= 4.2)
@@ -1078,7 +1078,7 @@ GEM
     truncato (0.7.11)
       htmlentities (~> 4.3.1)
       nokogiri (>= 1.7.0, <= 2.0)
-    tzinfo (1.2.6)
+    tzinfo (1.2.7)
       thread_safe (~> 0.1)
     u2f (0.2.1)
     uber (0.1.0)
@@ -1357,7 +1357,7 @@ DEPENDENCIES
   rouge (~> 3.18.0)
   rqrcode-rails3 (~> 0.1.7)
   rspec-parameterized
-  rspec-rails (~> 4.0.0.beta4)
+  rspec-rails (~> 4.0.0)
   rspec-retry (~> 0.6.1)
   rspec_junit_formatter
   rspec_profiling (~> 0.0.5)

spec/initializers/action_mailer_hooks_spec.rb

@@ -6,6 +6,10 @@ describe 'ActionMailer hooks' do
   describe 'smime signature interceptor' do
     before do
       class_spy(ActionMailer::Base).as_stubbed_const
+
+      # rspec-rails calls ActionMailer::Base.deliveries.clear after every test
+      # https://github.com/rspec/rspec-rails/commit/71c12388e2bad78aaeea6443a393ede78341a7a3
+      allow(ActionMailer::Base).to receive_message_chain(:deliveries, :clear)
     end
 
     it 'is disabled by default' do