Don't allow 'rubocop:check:graceful' Rake task to take paths

Signed-off-by: Rémy Coutable <remy@rymai.me>

rubocop/check_graceful_task.rb

@@ -15,17 +15,14 @@ def run(args)
         --format RuboCop::Formatter::GracefulFormatter
       ]
 
-      available_cops = RuboCop::Cop::Registry.global.to_h
-
-      cop_names, paths = args.partition { available_cops.key?(_1) }
+      # Convert from Rake::TaskArguments into an Array to make `any?` work as expected.
+      cop_names = args.to_a
 
       if cop_names.any?
         list = cop_names.sort.join(',')
         options.concat ['--only', list]
       end
 
-      options.concat(paths)
-
       puts <<~MSG
         Running RuboCop in graceful mode:
           rubocop #{options.join(' ')}

spec/rubocop/check_graceful_task_spec.rb

@@ -119,9 +119,9 @@
     end
 
     context 'with args' do
-      let(:args) { %w[a.rb Lint/EmptyFile b.rb Lint/Syntax] }
+      let(:args) { %w[Lint/EmptyFile Lint/Syntax] }
 
-      it_behaves_like 'rubocop scan', rubocop_args: %w[--only Lint/EmptyFile,Lint/Syntax a.rb b.rb]
+      it_behaves_like 'rubocop scan', rubocop_args: %w[--only Lint/EmptyFile,Lint/Syntax]
 
       it 'does not notify slack' do
         expect(Gitlab::Popen).not_to receive(:popen)