Fix feature category for the TestsController
This controller incorrectly inherited continuous_integration as the feature category from the Projects::Pipelines::ApplicationController. This fixes that so the metrics for this controller show up on the testing group's dashboard: https://dashboards.gitlab.net/d/stage-groups-testing/stage-groups-group-dashboard-verify-testing?orgId=1
Relates to gitlab-com/gl-infra/scalability#773 (closed)
Edited by Bob Van Landuyt