[E2E] PROMOTE TO BLOCKING: create_group_iteration_spec.rb

What does this MR do?

Promotes the following e2e tests to the blocking bucket:

1. Plan Group Iterations with manual scheduling creates a group iteration manually through an iteration cadence | Testcase | Spec metrics

2. Plan Group Iterations with automatic scheduling creates a group iteration automatically through an iteration cadence | Testcase | Spec metrics

This MR was created based on data from reliable e2e test report: #468608 (closed)

(This MR was automatically generated by gitlab_quality-test_tooling at 2024-06-24 02:05:30 UTC)