Remove `action_mailer.default_url_options` override in development

What does this MR do and why?

Developers could use different protocol/host/port in development.

For instance, I use https://gdk.test:3443. I noticed that links in emails point to http://localhost:3000.

This change should make links to be generated based on a developer's configs.

This setting is set by Rails.application.routes.default_url_options = default_url_options in config/initializers/default_url_options.rb

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How to set up and validate locally

https://docs.gitlab.com/ee/development/emails.html#mailer-previews

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