Adds tag push example to webhooks e2e spec

Description of the test

Adds a tag push event example to the project hooks e2e spec.

This is an orchestrated API test that should only run in the ee:integrations job.

The orchestrated environment is transient, so no resource handling happens in this spec.

To run the webhook spec locally against GDK:

cd qa && ./bin/qa Test::Instance::All http://127.0.0.1:3000 -- -t integrations qa/specs/features/api/1_manage/integrations/webhook_events_spec.rb

testcase: https://gitlab.com/gitlab-org/gitlab/-/quality/test_cases/383577

Checklist

• Confirm the test has a testcase: tag linking to an existing test case in the test case project.
• Note if the test is intended to run in specific scenarios. If a scenario is new, add a link to the MR that adds the new scenario.
• Follow the end-to-end tests style guide and best practices.
• Use the appropriate RSpec metadata tag(s).
• Most resources will be cleaned up via the general cleanup task. Check that is successful, or ensure resources are cleaned up in the test:
  • New resources have api_get_path and api_delete_path implemented if possible.
  • If any resource cannot be deleted in the general delete task, make sure it is ignored.
  • If any resource cannot be deleted in the general delete task, remove it in the test (e.g., in an after block).
• Ensure that no transient bugs are hidden accidentally due to the usage of waits and reloads.
• Verify the tags to ensure it runs on the desired test environments.
• If this MR has a dependency on another MR, such as a GitLab QA MR, specify the order in which the MRs should be merged.
• (If applicable) Create a follow-up issue to document the special setup necessary to run the test: ISSUE_LINK
• If the test requires an admin's personal access token, ensure that the test passes on your local environment with and without the GITLAB_QA_ADMIN_ACCESS_TOKEN provided.