Update Set-Cookie specs to match the date format set by newer rack versions

Author: andrehjr

spec/persistence/cookie_adapter_spec.rb

@@ -52,7 +52,7 @@
     it "puts multiple experiments in a single cookie" do
       subject["foo"] = "FOO"
       subject["bar"] = "BAR"
-      expect(context.response.headers["Set-Cookie"]).to match(/\Asplit=%7B%22foo%22%3A%22FOO%22%2C%22bar%22%3A%22BAR%22%7D; path=\/; expires=[a-zA-Z]{3}, \d{2} [a-zA-Z]{3} \d{4} \d{2}:\d{2}:\d{2} -0000\Z/)
+      expect(context.response.headers["Set-Cookie"]).to match(/\Asplit=%7B%22foo%22%3A%22FOO%22%2C%22bar%22%3A%22BAR%22%7D; path=\/; expires=[a-zA-Z]{3}, \d{2} [a-zA-Z]{3} \d{4} \d{2}:\d{2}:\d{2} [A-Z]{3}\Z/)
     end
 
     it "ensure other added cookies are not overriden" do