Hides Triggers if integration only has one event

Removes confusing/unnecessary checkboxes when trying to configure an
integration. If there is only one supported event we don't need to
allow these to be individually disabled since the integration can be
disabled instead.

E.g. Project Integrations for GitHub, Bugzilla, Asana, Pipeline emails and Gemnasium

app/models/service.rb

@@ -131,7 +131,14 @@ class Service < ActiveRecord::Base
   end
 
   def configurable_events
-    self.class.supported_events
+    events = self.class.supported_events
+
+    # No need to disable individual triggers when there is only one
+    if events.count == 1
+      []
+    else
+      events
+    end
   end
 
   def supported_events

ee/app/models/project_services/github_service.rb

@@ -38,10 +38,6 @@ class GithubService < Service
     %w(pipeline)
   end
 
-  def configurable_events
-    []
-  end
-
   def can_test?
     project.pipelines.any?
   end