Log Message:
devel/ruby-rspec-rails: update to 3.9.1

Update ruby-rspec-rails to 3.9.1.

### 3.9.1 / 2020-03-10
[Full Changelog](http://github.com/rspec/rspec-rails/compare/v3.9.0...v3.9.1)

Bug Fixes:

* Add missing require for have_enqueued_mail matcher. (Ignatius Reza, #2117)