Fix Drone CI service template not saving properly

Closes #3419

CHANGELOG

@@ -2,6 +2,7 @@ Please view this file on the master branch, on stable branches it's out of date.
 
 v 8.2.0 (unreleased)
   - Remove CSS property preventing hard tabs from rendering in Chromium 45 (Stan Hu)
+  - Fix Drone CI service template not saving properly (Stan Hu)
   - Added a GitLab specific profiling tool called "Sherlock" (see GitLab CE merge request #1749)
   - Upgrade gitlab_git to 7.2.20 and rugged to 0.23.3 (Stan Hu)
   - Improved performance of finding users by one of their Email addresses

app/models/project_services/drone_ci_service.rb

@@ -32,7 +32,6 @@ class DroneCiService < CiService
 
   def compose_service_hook
     hook = service_hook || build_service_hook
-    hook.url = [drone_url, "/api/hook", "?owner=#{project.namespace.path}", "&name=#{project.path}", "&access_token=#{token}"].join
     hook.enable_ssl_verification = enable_ssl_verification
     hook.save
   end