Use RSpec zero monkey patching mode

What does this Merge Request do?

Don't depend on RSpecs methods to be defined globally, so use RSpec.describe instead. Also disable it.

More info at: https://relishapp.com/rspec/rspec-core/docs/configuration/zero-monkey-patching-mode

Related to gitlab#220018 (closed)

Merge Request checklist

• Tests added for new functionality. If not, please raise Issue to follow-up.
• This change is backward compatible. If not, please include steps to communicate to our users.
• Documentation added/updated, if needed.
• gdk doctor test added, if needed.