Remove unneeded stages in the browser performance template

doc/user/project/merge_requests/browser_performance_testing.md

@@ -155,7 +155,7 @@ stages:
   - performance
 
 include:
-  template: Browser-Performance.gitlab-ci.yml
+  template: Verify/Browser-Performance.gitlab-ci.yml
 
 review:
   stage: deploy

lib/gitlab/ci/templates/Verify/Browser-Performance.gitlab-ci.yml

 # Read more about the feature here: https://docs.gitlab.com/ee/user/project/merge_requests/browser_performance_testing.html
 
 stages:
-  - build
-  - test
-  - deploy
   - performance
 
 performance: