Optimize a few simple spec files by using `set`

spec/models/abuse_report_spec.rb

 require 'rails_helper'
 
-RSpec.describe AbuseReport do
-  subject     { create(:abuse_report) }
-  let(:user)  { create(:admin) }
+describe AbuseReport do
+  set(:report) { create(:abuse_report) }
+  set(:user) { create(:admin) }
+  subject { report }
 
   it { expect(subject).to be_valid }
 

spec/models/appearance_spec.rb

 require 'rails_helper'
 
-RSpec.describe Appearance do
+describe Appearance do
   subject { build(:appearance) }
 
   it { is_expected.to be_valid }

spec/models/chat_name_spec.rb

 require 'spec_helper'
 
 describe ChatName do
-  subject { create(:chat_name) }
+  set(:chat_name) { create(:chat_name) }
+  subject { chat_name }
 
   it { is_expected.to belong_to(:service) }
   it { is_expected.to belong_to(:user) }

spec/models/chat_team_spec.rb

 require 'spec_helper'
 
 describe ChatTeam do
-  subject { create(:chat_team) }
+  set(:chat_team) { create(:chat_team) }
+  subject { chat_team }
 
   # Associations
   it { is_expected.to belong_to(:namespace) }