Avoid problem with peer dependency

rubocop-rspec_rails is a new dependency of rubocop-rspec.

Its HttpStatus cop only exists if the rake gem is present (!!!!!)

Causes this error:

    Error: unrecognized cop or department RSpecRails/HttpStatus found in
    .../gems/rubocop-rspec_rails-2.28.1/config/default.yml

Gemfile

@@ -6,7 +6,7 @@ group :development do
   gem "aruba", ">= 0.0.0"
   gem "pry-byebug"
   gem "rspec", ">= 3.0.0"
-  gem "rubocop-rspec"
+  gem "rubocop-rspec", "2.27.1"
   gem "simplecov"
   gem "webrick"
   gem "yard"