Forbid any type of metadata in RSpec shared_examples and shared_context
Related https://gitlab.com/gitlab-org/gitlab/-/issues/389268 and https://gitlab.com/gitlab-org/gitlab/-/merge_requests/116314#note_1337314756
Using metadata in shared examples is causing flaky tests.
## Proposal
We can do this using a Rubocop rule.
This one could be changed https://gitlab.com/gitlab-org/gitlab/-/merge_requests/115554
issue