Apply manual rubocop fixes

spec/policies/submission_policy_spec.rb

@@ -3,12 +3,12 @@
 require 'rails_helper'
 
 describe SubmissionPolicy do
-  subject { described_class }
+  subject(:policy) { described_class }
 
   permissions :create? do
     it 'grants access to anyone' do
       %i[admin external_user teacher].each do |factory_name|
-        expect(subject).to permit(FactoryBot.build(factory_name), Submission.new)
+        expect(policy).to permit(FactoryBot.build(factory_name), Submission.new)
       end
     end
   end
@@ -16,21 +16,21 @@ describe SubmissionPolicy do
   %i[download_file? render_file? run? score? show? statistics? stop? test?].each do |action|
     permissions(action) do
       it 'grants access to admins' do
-        expect(subject).to permit(FactoryBot.build(:admin), Submission.new)
+        expect(policy).to permit(FactoryBot.build(:admin), Submission.new)
       end
 
       it 'grants access to authors' do
         user = FactoryBot.create(:external_user)
-        expect(subject).to permit(user, FactoryBot.build(:submission, exercise: Exercise.new, user_id: user.id, user_type: user.class.name))
+        expect(policy).to permit(user, FactoryBot.build(:submission, exercise: Exercise.new, user_id: user.id, user_type: user.class.name))
       end
     end
   end
 
   permissions :index? do
     it 'grants access to admins only' do
-      expect(subject).to permit(FactoryBot.build(:admin), Submission.new)
+      expect(policy).to permit(FactoryBot.build(:admin), Submission.new)
       %i[external_user teacher].each do |factory_name|
-        expect(subject).not_to permit(FactoryBot.build(factory_name), Submission.new)
+        expect(policy).not_to permit(FactoryBot.build(factory_name), Submission.new)
       end
     end
   end