chore: Add action mailer to Gemfile, alphabetize

Author: kaylareopelle

instrumentation/rails/Gemfile

@@ -11,10 +11,11 @@ gemspec
 group :test, :development do
   gem 'pry-byebug'
   gem 'opentelemetry-instrumentation-base', path: '../base'
-  gem 'opentelemetry-instrumentation-action_pack', path: '../action_pack'
-  gem 'opentelemetry-instrumentation-action_view', path: '../action_view'
   gem 'opentelemetry-instrumentation-active_job', path: '../active_job'
+  gem 'opentelemetry-instrumentation-action_mailer', path: '../action_mailer'
+  gem 'opentelemetry-instrumentation-action_pack', path: '../action_pack'
   gem 'opentelemetry-instrumentation-active_record', path: '../active_record'
   gem 'opentelemetry-instrumentation-active_support', path: '../active_support'
+  gem 'opentelemetry-instrumentation-action_view', path: '../action_view'
   gem 'opentelemetry-instrumentation-rack', path: '../rack'
 end