Add Capybara::RSpecMatchers to some tests that should include it

spec/basic_node_spec.rb

@@ -3,6 +3,7 @@
 require 'spec_helper'
 
 RSpec.describe Capybara do
+  include Capybara::RSpecMatchers
   describe '.string' do
     let :string do
       described_class.string <<-STRING

spec/rack_test_spec.rb

@@ -38,6 +38,7 @@ Capybara::SpecHelper.run_specs TestSessions::RackTest, 'RackTest', capybara_skip
 end
 
 RSpec.describe Capybara::Session do # rubocop:disable RSpec/MultipleDescribes
+  include Capybara::RSpecMatchers
   context 'with rack test driver' do
     let(:session) { TestSessions::RackTest }
 

spec/selector_spec.rb

@@ -3,6 +3,7 @@
 require 'spec_helper'
 
 RSpec.describe Capybara do
+  include Capybara::RSpecMatchers
   describe 'Selectors' do
     let :string do
       described_class.string <<-STRING