Bump rubocop-rspec from 3.1.0 to 3.4.0

Note we're renaming the RSpec/StringAsInstanceDoubleConstant rule to
RSpec/VerifiedDoubleReference because its name changed in version 3.4.0

Bumps [rubocop-rspec](https://github.com/rubocop/rubocop-rspec) from 3.1.0 to 3.4.0.
- [Release notes](https://github.com/rubocop/rubocop-rspec/releases)
- [Changelog](https://github.com/rubocop/rubocop-rspec/blob/master/CHANGELOG.md)
- [Commits](https://github.com/rubocop/rubocop-rspec/compare/v3.1.0...v3.4.0)

---
updated-dependencies:
- dependency-name: rubocop-rspec
  dependency-type: direct:development
  update-type: version-update:semver-minor
...

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

.rubocop.yml

@@ -642,10 +642,10 @@ RSpec/SpecFilePathFormat:
 RSpec/SpecFilePathSuffix:
   Enabled: true
 
-RSpec/StringAsInstanceDoubleConstant:
+RSpec/UndescriptiveLiteralsDescription:
   Enabled: true
 
-RSpec/UndescriptiveLiteralsDescription:
+RSpec/VerifiedDoubleReference:
   Enabled: true
 
 RSpec/VoidExpect: