Allow newer versions of httparty to satisfy dependency

--- a/Gemfile
+++ b/Gemfile
@@ -239,7 +239,7 @@ gem 'gitlab-sidekiq-fetcher', '0.9.0', r
 gem 'fugit', '~> 1.8', '>= 1.8.1'
 
 # HTTP requests
-gem 'httparty', '~> 0.20.0'
+gem 'httparty', '~> 0.20'
 
 # Colored output to console
 gem 'rainbow', '~> 3.0'