Update group branch modification setting

What does this MR do and why?

Update group branch modification setting

• displays the setting for groups and SPPs that have groups linked to them (as confirmed by the PM)
• requests SPP linked groups
• add setting to setting list
• update yaml
• update tests

References

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MR acceptance checklist

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Screenshots or screen recordings

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Scenario	Screenshot
SPP w/o groups linked
SPP w/ groups linked	np_-project-_groups_linked_small

How to set up and validate locally

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

1. Upload a GitLab Ultimate license
2. Enable the feature flag echo "Feature.enable(:scan_result_policy_block_group_branch_modification)" | rails c
3. Navigate to a project => Secure => Policies => New policy => Merge request approval policy
4. Verify the Block group branch modification setting does not show
5. Navigate to a group => Secure => Policies => New policy => Merge request approval policy
6. Verify the Block group branch modification setting shows and can be toggled and modified
7. Create the policy
8. Navigate to the new SPP created => Secure => Policies => New policy => Merge request approval policy
9. Verify the Block group branch modification setting does show
10. Modify it and create the policy
11. Navigate to the project => Secure => Policies => Select the policy => Edit policy
12. Verify the policy editor shows the setting

Related to #435725 (closed)