ci: Don't set 'feature_category' on shared examples

What does this MR do and why?

Shared examples must not have a :feature_category metadata since that would automatically include these to all examples with the same :feature_category.

How to set up and validate locally

Numbered steps to set up and validate the change are strongly suggested.

Steps from #389268 (closed) can be followed.

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.

Related to #389268 (closed).