Use `Rails.env.local?` shorthand method to check env (#27519)

app/models/user.rb

@@ -488,7 +488,7 @@ class User < ApplicationRecord
   end
 
   def validate_email_dns?
-    email_changed? && !external? && !(Rails.env.test? || Rails.env.development?)
+    email_changed? && !external? && !Rails.env.local? # rubocop:disable Rails/UnknownEnv
   end
 
   def validate_role_elevation

config/application.rb

@@ -206,7 +206,7 @@ module Mastodon
     # We use our own middleware for this
     config.public_file_server.enabled = false
 
-    config.middleware.use PublicFileServerMiddleware if Rails.env.development? || Rails.env.test? || ENV['RAILS_SERVE_STATIC_FILES'] == 'true'
+    config.middleware.use PublicFileServerMiddleware if Rails.env.local? || ENV['RAILS_SERVE_STATIC_FILES'] == 'true' # rubocop:disable Rails/UnknownEnv
     config.middleware.use Rack::Attack
     config.middleware.use Mastodon::RackMiddleware