Suppress RuboCop's offenses

This commit suppresses the following RuboCop's offenses:

```console
$ bundle exec rubocop -a
Inspecting 25 files
....................C....

Offenses:

spec/rubocop/cop/rake/desc_spec.rb:4:6: C: [Corrected] InternalAffairs/ExampleDescription: Description does not match use of expect_offense.
  it 'register an offense for task on the top level' do
     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
spec/rubocop/cop/rake/desc_spec.rb:16:6: C: [Corrected] InternalAffairs/ExampleDescription: Description does not match use of expect_offense.
  it 'register an offense for task with block in a block' do
     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
spec/rubocop/cop/rake/desc_spec.rb:33:6: C: [Corrected] InternalAffairs/ExampleDescription: Description does not match use of expect_offense.
  it 'register an offense for task in kwbegin' do
     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

25 files inspected, 3 offenses detected, 3 offenses corrected
```

spec/rubocop/cop/rake/desc_spec.rb

@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
 RSpec.describe RuboCop::Cop::Rake::Desc, :config do
-  it 'register an offense for task on the top level' do
+  it 'registers an offense for task on the top level' do
     expect_offense(<<~RUBY)
       task :foo
       ^^^^^^^^^ Describe the task with `desc` method.
@@ -13,7 +13,7 @@
     RUBY
   end
 
-  it 'register an offense for task with block in a block' do
+  it 'registers an offense for task with block in a block' do
     expect_offense(<<~RUBY)
       tap do
         task :foo
@@ -30,7 +30,7 @@
     RUBY
   end
 
-  it 'register an offense for task in kwbegin' do
+  it 'registers an offense for task in kwbegin' do
     expect_offense(<<~RUBY)
       begin
         task :foo