DEV: Replace deprecated queue_jobs site setting in tests (discourse#88)

The #queue_jobs= method on site settings has been deprecated and replaced by Jobs.run_later! and Jobs.run_immediately!. This PR replaces usages in this plugin so we can remove the fallback in core.

Author: Drenmi

spec/plugin_spec.rb

@@ -128,7 +128,7 @@
 
     describe "avatar downloading" do
       before do
-        SiteSetting.queue_jobs = true
+        Jobs.run_later!
         SiteSetting.oauth2_fetch_user_details = true
         SiteSetting.oauth2_email_verified = true
       end