Apply automatic rubocop fixes

spec/mailers/previews/user_mailer_preview.rb

@@ -1,5 +1,7 @@
+# frozen_string_literal: true
+
 class UserMailerPreview < ActionMailer::Preview
-  def exercise_anomaly_detected()
+  def exercise_anomaly_detected
     collection = ExerciseCollection.new(name: 'Hello World', user: FactoryBot.create(:admin))
     anomalies = {49 => 879.325828, 51 => 924.870057, 31 => 1031.21233, 69 => 2159.182116}
     UserMailer.exercise_anomaly_detected(collection, anomalies)

spec/mailers/user_mailer_spec.rb

@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'rails_helper'
 
 describe UserMailer do
@@ -6,7 +8,7 @@ describe UserMailer do
   describe '#activation_needed_email' do
     let(:mail) { described_class.activation_needed_email(user) }
 
-    before(:each) do
+    before do
       user.send(:setup_activation)
       user.save(validate: false)
     end
@@ -37,7 +39,7 @@ describe UserMailer do
   describe '#reset_password_email' do
     let(:mail) { described_class.reset_password_email(user) }
 
-    before(:each) do
+    before do
       user.send(:setup_activation)
       user.save(validate: false)
     end