Bump rubocop-rspec from 2.14.2 to 2.15.0

Bumps [rubocop-rspec](https://github.com/rubocop/rubocop-rspec) from 2.14.2 to 2.15.0.
- [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/v2.14.2...v2.15.0)

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

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

Gemfile.lock

@@ -213,7 +213,7 @@ GEM
       rspec-mocks (~> 3.11)
       rspec-support (~> 3.11)
     rspec-support (3.11.1)
-    rubocop (1.37.1)
+    rubocop (1.38.0)
       json (~> 2.3)
       parallel (~> 1.10)
       parser (>= 3.1.2.1)
@@ -229,7 +229,7 @@ GEM
       activesupport (>= 4.2.0)
       rack (>= 1.1)
       rubocop (>= 1.33.0, < 2.0)
-    rubocop-rspec (2.14.2)
+    rubocop-rspec (2.15.0)
       rubocop (~> 1.33)
     ruby-progressbar (1.11.0)
     ruby-vips (2.1.4)