Update performance issue links and thresholds (!351) · Merge requests · GitLab.org / Quality Department / GitLab Performance Tool

The MR updates links and thresholds for some endpoints that were improved in %14.0

k6/tests/api/api_v4_projects_merge_requests.js -> new issue gitlab-org/gitlab#332392 (closed)
k6/tests/web/web_project_branches.js -> new issue gitlab-org/gitlab#332498
k6/tests/web/web_project_file_rendered.js -> new issue gitlab-org/gitlab#332499

Update performance issue links and thresholds