Configure SimpleCov as recommended by author

The configuration can go into the central .simplecov file and then we
just need to `require` simplecov to start the coverage process. This
also avoids duplicating the config if we want to start simplecov from
the rails server to cover the lines used in by the server in feature
specs.

https://github.com/simplecov-ruby/simplecov#using-simplecov-for-centralized-config

.simplecov

@@ -0,0 +1,18 @@
+#!/bin/env ruby
+
+SimpleCov.start 'rails' do
+  minimum_coverage 54
+
+  add_filter '/bin/'
+  add_filter '/config/'
+  add_filter '/jobs/application_job.rb'
+  add_filter '/schemas/'
+  add_filter '/lib/generators'
+  add_filter '/spec/'
+  add_filter '/vendor/'
+  add_filter '/public'
+  add_filter '/swagger'
+  add_filter '/script'
+  add_filter '/log'
+  add_filter '/db'
+end

spec/coverage_helper.rb

@@ -1,21 +0,0 @@
-# frozen_string_literal: true
-
-if ENV["COVERAGE"]
-  require 'simplecov'
-
-  SimpleCov.minimum_coverage 54
-  SimpleCov.start 'rails' do
-    add_filter '/bin/'
-    add_filter '/config/'
-    add_filter '/jobs/application_job.rb'
-    add_filter '/schemas/'
-    add_filter '/lib/generators'
-    add_filter '/spec/'
-    add_filter '/vendor/'
-    add_filter '/public'
-    add_filter '/swagger'
-    add_filter '/script'
-    add_filter '/log'
-    add_filter '/db'
-  end
-end

spec/spec_helper.rb

@@ -1,9 +1,6 @@
 # frozen_string_literal: true
 
-if ENV["COVERAGE"]
-  require 'simplecov'
-  SimpleCov.start 'rails'
-end
+require 'simplecov' if ENV["COVERAGE"]
 
 require 'rubygems'
 
@@ -24,7 +21,6 @@ require 'rspec/rails'
 require 'capybara'
 require 'database_cleaner'
 require 'rspec/retry'
-require 'coverage_helper'
 require 'paper_trail/frameworks/rspec'
 
 require 'webdrivers'