Revert "Document Rails::Generators::MailerGenerator"

This reverts commit dfb69f2b8a85586ad70071baba416747cbb07364.

Reason: Let's not nodoc without reason.

[ci skip]
Revert "nodoc ActionMailer module from lib/action_mailer/*.rb"

This reverts commit 328e876a1569058e47eaf7ea3f4f045a83b585fa.

Reason: Let's not nodoc without reason.

[ci skip]
Revert "ActionMailer::Collector should be nodoc'd"

This reverts commit e47c85c696de1c4137c222bedc846b2cdbb0893f.

Reason: Let's not nodoc without reason.

[ci skip]