Update rest-client requirement from ~> 1.8 to >= 1.8, < 3.0

Updates the requirements on [rest-client](https://github.com/rest-client/rest-client) to permit the latest version.
- [Release notes](https://github.com/rest-client/rest-client/releases)
- [Changelog](https://github.com/rest-client/rest-client/blob/master/history.md)
- [Commits](https://github.com/rest-client/rest-client/commits/v1.8.0)

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

calagator.gemspec

@@ -41,7 +41,7 @@ Gem::Specification.new do |s|
   s.add_dependency "rack-contrib", "~> 1.0"
   s.add_dependency "rails-observers"
   s.add_dependency "rails_autolink", "~> 1.1"
-  s.add_dependency "rest-client", "~> 1.8"
+  s.add_dependency "rest-client", ">= 1.8", "< 3.0"
   s.add_dependency "ri_cal", "~> 0.8.8"
   s.add_dependency "sass", "~> 3.2"
   s.add_dependency "sass-rails"