Update vagrant in Gemfile

Gemfile

@@ -6,7 +6,7 @@ group :development do
   # We depend on Vagrant for development, but we don't add it as a
   # gem dependency because we expect to be installed within the
   # Vagrant environment itself using `vagrant plugin`.
-  gem "vagrant", :git => "https://github.com/mitchellh/vagrant.git", :ref => 'v2.2.6'
+  gem "vagrant", :git => "https://github.com/mitchellh/vagrant.git", :ref => 'v2.2.7'
 end
 
 group :plugins do