Bump rspec-rails from 3.9.0 to 3.9.1

Bumps [rspec-rails](https://github.com/rspec/rspec-rails) from 3.9.0 to 3.9.1.
- [Release notes](https://github.com/rspec/rspec-rails/releases)
- [Changelog](https://github.com/rspec/rspec-rails/blob/master/Changelog.md)
- [Commits](https://github.com/rspec/rspec-rails/compare/v3.9.0...v3.9.1)

Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

Gemfile.lock

@@ -306,7 +306,7 @@ GEM
     rspec-mocks (3.9.1)
       diff-lcs (>= 1.2.0, < 2.0)
       rspec-support (~> 3.9.0)
-    rspec-rails (3.9.0)
+    rspec-rails (3.9.1)
       actionpack (>= 3.0)
       activesupport (>= 3.0)
       railties (>= 3.0)