Merge pull request #30416 from yhirano55/use_tt_in_doc_for_action_mailer

Use tt in doc for action_mailer [ci skip]

actionmailer/lib/action_mailer/rescuable.rb

 # frozen_string_literal: true
 
 module ActionMailer #:nodoc:
-  # Provides `rescue_from` for mailers. Wraps mailer action processing,
+  # Provides +rescue_from+ for mailers. Wraps mailer action processing,
   # mail job processing, and mail delivery.
   module Rescuable
     extend ActiveSupport::Concern