Suppress new Style/RedundantHeredocDelimiterQuotes cop's offenses

Follow up rubocop/rubocop#11528.

This commit suppresses the following new `Style/RedundantHeredocDelimiterQuotes` cop's offenses:

```console
% bundle exec rake
(snip)

Offenses:

spec/rubocop/cop/rails/helper_instance_variable_spec.rb:31:24:
C: [Correctable] Style/RedundantHeredocDelimiterQuotes: Remove the redundant heredoc delimiter quotes, use <<~RUBY instead.
    expect_no_offenses(<<~'RUBY')
                       ^^^^^^^^^
spec/rubocop/cop/rails/helper_instance_variable_spec.rb:39:24:
C: [Correctable] Style/RedundantHeredocDelimiterQuotes: Remove the redundant heredoc delimiter quotes, use <<~RUBY instead.
    expect_no_offenses(<<~'RUBY')
                       ^^^^^^^^^
spec/rubocop/cop/rails/helper_instance_variable_spec.rb:50:24:
C: [Correctable] Style/RedundantHeredocDelimiterQuotes: Remove the redundant heredoc delimiter quotes, use <<~RUBY instead.
    expect_no_offenses(<<~'RUBY')
                       ^^^^^^^^^
spec/rubocop/cop/rails/helper_instance_variable_spec.rb:61:20:
C: [Correctable] Style/RedundantHeredocDelimiterQuotes: Remove the redundant heredoc delimiter quotes, use <<~RUBY instead.
    expect_offense(<<~'RUBY')
                   ^^^^^^^^^
spec/rubocop/cop/rails/match_route_spec.rb:110:24:
C: [Correctable] Style/RedundantHeredocDelimiterQuotes: Remove the redundant heredoc delimiter quotes, use <<~RUBY instead.
    expect_no_offenses(<<~'RUBY')
                       ^^^^^^^^^
spec/rubocop/cop/rails/reflection_class_name_spec.rb:57:24:
C: [Correctable] Style/RedundantHeredocDelimiterQuotes: Remove the redundant heredoc delimiter quotes, use <<~RUBY instead.
    expect_no_offenses(<<~'RUBY')
                       ^^^^^^^^^
spec/rubocop/cop/rails/reflection_class_name_spec.rb:63:24:
C: [Correctable] Style/RedundantHeredocDelimiterQuotes: Remove the redundant heredoc delimiter quotes, use <<~RUBY instead.
    expect_no_offenses(<<~'RUBY')
                       ^^^^^^^^^
spec/rubocop/cop/rails/root_pathname_methods_spec.rb:123:22:
C: [Correctable] Style/RedundantHeredocDelimiterQuotes: Remove the redundant heredoc delimiter quotes, use <<~RUBY instead.
      expect_offense(<<~'RUBY')
                     ^^^^^^^^^

279 files inspected, 8 offenses detected, 8 offenses autocorrectable
```

Author: koic

spec/rubocop/cop/rails/helper_instance_variable_spec.rb

@@ -28,15 +28,15 @@ def welcome_message(user)
   end
 
   it 'does not register an offense when using memoization' do
-    expect_no_offenses(<<~'RUBY')
+    expect_no_offenses(<<~RUBY)
       def foo
         @cache ||= heavy_load
       end
     RUBY
   end
 
   it 'does not register an offense when a class which inherits `ActionView::Helpers::FormBuilder`' do
-    expect_no_offenses(<<~'RUBY')
+    expect_no_offenses(<<~RUBY)
       class MyFormBuilder < ActionView::Helpers::FormBuilder
         def do_something
           @template
@@ -47,7 +47,7 @@ def do_something
   end
 
   it 'does not register an offense when a class which inherits `::ActionView::Helpers::FormBuilder`' do
-    expect_no_offenses(<<~'RUBY')
+    expect_no_offenses(<<~RUBY)
       class MyFormBuilder < ::ActionView::Helpers::FormBuilder
         def do_something
           @template
@@ -58,7 +58,7 @@ def do_something
   end
 
   it 'registers an offense when using a class which does not inherit `ActionView::Helpers::FormBuilder`' do
-    expect_offense(<<~'RUBY')
+    expect_offense(<<~RUBY)
       class Foo
         def do_something
           @template

spec/rubocop/cop/rails/match_route_spec.rb

@@ -107,7 +107,7 @@
   end
 
   it 'does not register an offense when via is a variable' do
-    expect_no_offenses(<<~'RUBY')
+    expect_no_offenses(<<~RUBY)
       routes.draw do
         match ':controller/:action/:id', via: method
       end

spec/rubocop/cop/rails/reflection_class_name_spec.rb

@@ -54,13 +54,13 @@
   end
 
   it 'does not register an offense when using `class_name: do_something.to_s`' do
-    expect_no_offenses(<<~'RUBY')
+    expect_no_offenses(<<~RUBY)
       has_many :accounts, class_name: do_something.to_s
     RUBY
   end
 
   it 'does not register an offense when using `class_name: to_s`' do
-    expect_no_offenses(<<~'RUBY')
+    expect_no_offenses(<<~RUBY)
       has_many :accounts, class_name: to_s
     RUBY
   end

spec/rubocop/cop/rails/root_pathname_methods_spec.rb

@@ -120,7 +120,7 @@
     end
 
     it 'registers an offense when using `Rails.env` argument within `Dir.glob`' do
-      expect_offense(<<~'RUBY')
+      expect_offense(<<~RUBY)
         Dir.glob(Rails.root.join("db", "seeds", Rails.env, "*.rb")).sort.each do |file|
         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `Rails.root` is a `Pathname` so you can just append `#glob`.
           load file